diff --git a/src/libraries/System.Numerics.Vectors/tests/GenericVectorTests.cs b/src/libraries/System.Numerics.Vectors/tests/GenericVectorTests.cs
index 14b1a2ec62833..dc13ea9c1117b 100644
--- a/src/libraries/System.Numerics.Vectors/tests/GenericVectorTests.cs
+++ b/src/libraries/System.Numerics.Vectors/tests/GenericVectorTests.cs
@@ -4546,7 +4546,7 @@ public void CosDoubleTest(double value, double expectedResult, double variance)
 
         [Theory]
         [MemberData(nameof(GenericMathTestMemberData.CosSingle), MemberType = typeof(GenericMathTestMemberData))]
-        public void CosCosgleTest(float value, float expectedResult, float variance)
+        public void CosSingleTest(float value, float expectedResult, float variance)
         {
             Vector<float> actualResult = Vector.Cos(Vector.Create(value));
             AssertEqual(Vector.Create(expectedResult), actualResult, Vector.Create(variance));
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs
index 70c28d0924a83..27bd7c10fa3e0 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector128.cs
@@ -3207,7 +3207,7 @@ public static Vector128<double> Sin(Vector128<double> vector)
         {
             if (IsHardwareAccelerated)
             {
-                return VectorMath.CosDouble<Vector128<double>, Vector128<long>>(vector);
+                return VectorMath.SinDouble<Vector128<double>, Vector128<long>>(vector);
             }
             else
             {
@@ -3226,11 +3226,11 @@ public static Vector128<float> Sin(Vector128<float> vector)
             {
                 if (Vector256.IsHardwareAccelerated)
                 {
-                    return VectorMath.CosSingle<Vector128<float>, Vector128<int>, Vector256<double>, Vector256<long>>(vector);
+                    return VectorMath.SinSingle<Vector128<float>, Vector128<int>, Vector256<double>, Vector256<long>>(vector);
                 }
                 else
                 {
-                    return VectorMath.CosSingle<Vector128<float>, Vector128<int>, Vector128<double>, Vector128<long>>(vector);
+                    return VectorMath.SinSingle<Vector128<float>, Vector128<int>, Vector128<double>, Vector128<long>>(vector);
                 }
             }
             else
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs
index c90524a56bdee..eb2aa61fce4ed 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector256.cs
@@ -3090,7 +3090,7 @@ public static Vector256<double> Sin(Vector256<double> vector)
         {
             if (IsHardwareAccelerated)
             {
-                return VectorMath.CosDouble<Vector256<double>, Vector256<long>>(vector);
+                return VectorMath.SinDouble<Vector256<double>, Vector256<long>>(vector);
             }
             else
             {
@@ -3109,11 +3109,11 @@ public static Vector256<float> Sin(Vector256<float> vector)
             {
                 if (Vector512.IsHardwareAccelerated)
                 {
-                    return VectorMath.CosSingle<Vector256<float>, Vector256<int>, Vector512<double>, Vector512<long>>(vector);
+                    return VectorMath.SinSingle<Vector256<float>, Vector256<int>, Vector512<double>, Vector512<long>>(vector);
                 }
                 else
                 {
-                    return VectorMath.CosSingle<Vector256<float>, Vector256<int>, Vector256<double>, Vector256<long>>(vector);
+                    return VectorMath.SinSingle<Vector256<float>, Vector256<int>, Vector256<double>, Vector256<long>>(vector);
                 }
             }
             else
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector512.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector512.cs
index f5d3c0c1b9d6c..8f12942a7cfc5 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector512.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/Vector512.cs
@@ -3131,7 +3131,7 @@ public static Vector512<double> Sin(Vector512<double> vector)
         {
             if (IsHardwareAccelerated)
             {
-                return VectorMath.CosDouble<Vector512<double>, Vector512<long>>(vector);
+                return VectorMath.SinDouble<Vector512<double>, Vector512<long>>(vector);
             }
             else
             {
@@ -3148,7 +3148,7 @@ public static Vector512<float> Sin(Vector512<float> vector)
         {
             if (IsHardwareAccelerated)
             {
-                return VectorMath.CosSingle<Vector512<float>, Vector512<int>, Vector512<double>, Vector512<long>>(vector);
+                return VectorMath.SinSingle<Vector512<float>, Vector512<int>, Vector512<double>, Vector512<long>>(vector);
             }
             else
             {
diff --git a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/VectorMath.cs b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/VectorMath.cs
index 066deab0dc410..cf8df6927558f 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/VectorMath.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Runtime/Intrinsics/VectorMath.cs
@@ -211,30 +211,29 @@ public static TVectorSingle CosSingle<TVectorSingle, TVectorInt32, TVectorDouble
             const int ARG_SMALLER = 0x39000000; // 2^-27
 
             TVectorSingle ax = TVectorSingle.Abs(x);
-            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(x);
+            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(ax);
 
             TVectorSingle result;
 
-            if (TVectorSingle.LessThanOrEqualAll(ax, TVectorSingle.Create(ARG_LARGE)))
+            if (TVectorInt32.LessThanOrEqualAll(ux, TVectorInt32.Create(ARG_LARGE)))
             {
                 // We must be a finite value: (pi / 4) >= |x|
 
                 if (TVectorInt32.GreaterThanAny(ux, TVectorInt32.Create(ARG_SMALL - 1)))
                 {
                     // at least one element is: |x| >= 2^-13
-                    TVectorSingle x2 = x * x;
 
                     if (TVectorSingle.Count == TVectorDouble.Count)
                     {
                         result = Narrow<TVectorDouble, TVectorSingle>(
-                            CosSingleSmall(Widen<TVectorSingle, TVectorDouble>(x2))
+                            CosSingleSmall(Widen<TVectorSingle, TVectorDouble>(x))
                         );
                     }
                     else
                     {
                         result = Narrow<TVectorDouble, TVectorSingle>(
-                            CosSingleSmall(WidenLower<TVectorSingle, TVectorDouble>(x2)),
-                            CosSingleSmall(WidenUpper<TVectorSingle, TVectorDouble>(x2))
+                            CosSingleSmall(WidenLower<TVectorSingle, TVectorDouble>(x)),
+                            CosSingleSmall(WidenUpper<TVectorSingle, TVectorDouble>(x))
                         );
                     }
                 }
@@ -1760,8 +1759,8 @@ public static (TVectorDouble Sin, TVectorDouble Cos) SinCosDouble<TVectorDouble,
 
                 sinResult = TVectorDouble.ConditionalSelect(
                     Unsafe.BitCast<TVectorInt64, TVectorDouble>(TVectorInt64.Equals(((sign & region) | (~sign & ~region)) & TVectorInt64.One, TVectorInt64.Zero)),
-                    -sinResult, // negative in region 1 or 3, positive in region 0 or 2
-                    +sinResult  // negative in region 0 or 2, positive in region 1 or 3
+                    +sinResult, // negative in region 1 or 3, positive in region 0 or 2
+                    -sinResult  // negative in region 0 or 2, positive in region 1 or 3
                 );
 
                 cosResult = TVectorDouble.ConditionalSelect(
@@ -1806,12 +1805,12 @@ public static (TVectorDouble Sin, TVectorDouble Cos) SinCosDouble<TVectorDouble,
             sinResult = TVectorDouble.ConditionalSelect(
                 argNotSmallerMask,
                 sinResult,          // for elements: |x| >= 2^-27, infinity, or NaN
-                TVectorDouble.One   // for elements: 2^-27 > |x|
+                x                   // for elements: 2^-27 > |x|
             );
 
             cosResult = TVectorDouble.ConditionalSelect(
                 argNotSmallerMask,
-                cosResult,             // for elements: |x| >= 2^-27, infinity, or NaN
+                cosResult,          // for elements: |x| >= 2^-27, infinity, or NaN
                 TVectorDouble.One   // for elements: 2^-27 > |x|
             );
 
@@ -1838,11 +1837,11 @@ public static (TVectorSingle Sin, TVectorSingle Cos) SinCosSingle<TVectorSingle,
             const int ARG_SMALLER = 0x39000000; // 2^-27
 
             TVectorSingle ax = TVectorSingle.Abs(x);
-            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(x);
+            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(ax);
 
             TVectorSingle sinResult, cosResult;
 
-            if (TVectorSingle.LessThanOrEqualAll(ax, TVectorSingle.Create(ARG_LARGE)))
+            if (TVectorInt32.LessThanOrEqualAll(ux, TVectorInt32.Create(ARG_LARGE)))
             {
                 // We must be a finite value: (pi / 4) >= |x|
 
@@ -1945,7 +1944,7 @@ public static (TVectorSingle Sin, TVectorSingle Cos) SinCosSingle<TVectorSingle,
             sinResult = TVectorSingle.ConditionalSelect(
                 argNotSmallerMask,
                 sinResult,          // for elements: |x| >= 2^-27, infinity, or NaN
-                TVectorSingle.One   // for elements: 2^-27 > |x|
+                x                   // for elements: 2^-27 > |x|
             );
 
             cosResult = TVectorSingle.ConditionalSelect(
@@ -1982,8 +1981,8 @@ public static (TVectorSingle Sin, TVectorSingle Cos) SinCosSingle<TVectorSingle,
 
                 sinResult = TVectorDouble.ConditionalSelect(
                     Unsafe.BitCast<TVectorInt64, TVectorDouble>(TVectorInt64.Equals(((sign & region) | (~sign & ~region)) & TVectorInt64.One, TVectorInt64.Zero)),
-                    -sinResult, // negative in region 1 or 3, positive in region 0 or 2
-                    +sinResult  // negative in region 0 or 2, positive in region 1 or 3
+                    +sinResult, // negative in region 1 or 3, positive in region 0 or 2
+                    -sinResult  // negative in region 0 or 2, positive in region 1 or 3
                 );
 
                 cosResult = TVectorDouble.ConditionalSelect(
@@ -2095,8 +2094,8 @@ public static TVectorDouble SinDouble<TVectorDouble, TVectorInt64>(TVectorDouble
 
                 result = TVectorDouble.ConditionalSelect(
                     Unsafe.BitCast<TVectorInt64, TVectorDouble>(TVectorInt64.Equals(((sign & region) | (~sign & ~region)) & TVectorInt64.One, TVectorInt64.Zero)),
-                    -result,    // negative in region 1 or 3, positive in region 0 or 2
-                    +result     // negative in region 0 or 2, positive in region 1 or 3
+                    +result,    // negative in region 1 or 3, positive in region 0 or 2
+                    -result     // negative in region 0 or 2, positive in region 1 or 3
                 );
 
                 // Propagate the NaN that was passed in
@@ -2116,8 +2115,8 @@ public static TVectorDouble SinDouble<TVectorDouble, TVectorInt64>(TVectorDouble
 
             return TVectorDouble.ConditionalSelect(
                 Unsafe.BitCast<TVectorInt64, TVectorDouble>(TVectorInt64.GreaterThan(ux, TVectorInt64.Create(ARG_SMALLER - 1))),
-                result,             // for elements: |x| >= 2^-27, infinity, or NaN
-                TVectorDouble.One   // for elements: 2^-27 > |x|
+                result,     // for elements: |x| >= 2^-27, infinity, or NaN
+                x           // for elements: 2^-27 > |x|
             );
         }
 
@@ -2183,11 +2182,11 @@ public static TVectorSingle SinSingle<TVectorSingle, TVectorInt32, TVectorDouble
             const int ARG_SMALLER = 0x39000000; // 2^-27
 
             TVectorSingle ax = TVectorSingle.Abs(x);
-            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(x);
+            TVectorInt32 ux = Unsafe.BitCast<TVectorSingle, TVectorInt32>(ax);
 
             TVectorSingle result;
 
-            if (TVectorSingle.LessThanOrEqualAll(ax, TVectorSingle.Create(ARG_LARGE)))
+            if (TVectorInt32.LessThanOrEqualAll(ux, TVectorInt32.Create(ARG_LARGE)))
             {
                 // We must be a finite value: (pi / 4) >= |x|
 
@@ -2251,8 +2250,8 @@ public static TVectorSingle SinSingle<TVectorSingle, TVectorInt32, TVectorDouble
 
             return TVectorSingle.ConditionalSelect(
                 Unsafe.BitCast<TVectorInt32, TVectorSingle>(TVectorInt32.GreaterThan(ux, TVectorInt32.Create(ARG_SMALLER - 1))),
-                result,             // for elements: |x| >= 2^-27, infinity, or NaN
-                TVectorSingle.One   // for elements: 2^-27 > |x|
+                result,     // for elements: |x| >= 2^-27, infinity, or NaN
+                x           // for elements: 2^-27 > |x|
             );
 
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -2274,8 +2273,8 @@ static TVectorDouble CoreImpl(TVectorDouble x)
 
                 return TVectorDouble.ConditionalSelect(
                     Unsafe.BitCast<TVectorInt64, TVectorDouble>(TVectorInt64.Equals(((sign & region) | (~sign & ~region)) & TVectorInt64.One, TVectorInt64.Zero)),
-                    -result,    // negative in region 1 or 3, positive in region 0 or 2
-                    +result     // negative in region 0 or 2, positive in region 1 or 3
+                    +result,    // negative in region 1 or 3, positive in region 0 or 2
+                    -result     // negative in region 0 or 2, positive in region 1 or 3
                 );
             }
         }