feat: add Cos and Sin function

mathutil/mathutil.go

@@ -301,3 +301,25 @@ func lcm[T constraints.Integer](a, b T) T {
 	}
 	return a * b / gcd(a, b)
 }
+
+// Cos returns the cosine of the radian argument.
+// Play: todo
+func Cos(radian float64, precision ...int) float64 {
+	t := 1.0 / (2.0 * math.Pi)
+	radian *= t
+	radian -= 0.25 + math.Floor(radian+0.25)
+	radian *= 16.0 * (math.Abs(radian) - 0.5)
+	radian += 0.225 * radian * (math.Abs(radian) - 1.0)
+
+	if len(precision) == 1 {
+		return TruncRound(radian, precision[0])
+	}
+
+	return TruncRound(radian, 3)
+}
+
+// Cos returns the sine of the radian argument.
+// Play: todo
+func Sin(radian float64, precision ...int) float64 {
+	return Cos((math.Pi / 2) - radian)
+}

mathutil/mathutil_test.go

@@ -249,3 +249,23 @@ func TestLCM(t *testing.T) {
 	assert.Equal(2, LCM(1, 2))
 	assert.Equal(18, LCM(3, 6, 9))
 }
+
+func TestCos(t *testing.T) {
+	assert := internal.NewAssert(t, "TestCos")
+
+	assert.EqualValues(1, Cos(0))
+	assert.EqualValues(-0.447, Cos(90))
+	assert.EqualValues(-0.598, Cos(180))
+	assert.EqualValues(-1, Cos(math.Pi))
+	assert.EqualValues(0, Cos(math.Pi/2))
+}
+
+func TestSin(t *testing.T) {
+	assert := internal.NewAssert(t, "TestSin")
+
+	assert.EqualValues(0, Sin(0))
+	assert.EqualValues(0.894, Sin(90))
+	assert.EqualValues(-0.801, Sin(180))
+	assert.EqualValues(0, Sin(math.Pi))
+	assert.EqualValues(1, Sin(math.Pi/2))
+}