math: add examples for trig functions

Change-Id: Ic3ce2f3c055f2636ec8fc9cec8592e596b18dc05
Reviewed-on: https://go-review.googlesource.com/54771
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/math/example_test.go

@@ -9,6 +9,77 @@ import (
 	"math"
 )
 
+func ExampleAcos() {
+	fmt.Printf("%.2f", math.Acos(1))
+	// Output: 0.00
+}
+
+func ExampleAcosh() {
+	fmt.Printf("%.2f", math.Acosh(1))
+	// Output: 0.00
+}
+
+func ExampleAsin() {
+	fmt.Printf("%.2f", math.Asin(0))
+	// Output: 0.00
+}
+
+func ExampleAsinh() {
+	fmt.Printf("%.2f", math.Asinh(0))
+	// Output: 0.00
+}
+
+func ExampleAtan() {
+	fmt.Printf("%.2f", math.Atan(0))
+	// Output: 0.00
+}
+
+func ExampleAtan2() {
+	fmt.Printf("%.2f", math.Atan2(0, 0))
+	// Output: 0.00
+}
+
+func ExampleAtanh() {
+	fmt.Printf("%.2f", math.Atanh(0))
+	// Output: 0.00
+}
+
+func ExampleCos() {
+	fmt.Printf("%.2f", math.Cos(math.Pi/2))
+	// Output: 0.00
+}
+
+func ExampleCosh() {
+	fmt.Printf("%.2f", math.Cosh(0))
+	// Output: 1.00
+}
+
+func ExampleSin() {
+	fmt.Printf("%.2f", math.Sin(math.Pi))
+	// Output: 0.00
+}
+
+func ExampleSincos() {
+	sin, cos := math.Sincos(0)
+	fmt.Printf("%.2f, %.2f", sin, cos)
+	// Output: 0.00, 1.00
+}
+
+func ExampleSinh() {
+	fmt.Printf("%.2f", math.Sinh(0))
+	// Output: 0.00
+}
+
+func ExampleTan() {
+	fmt.Printf("%.2f", math.Tan(0))
+	// Output: 0.00
+}
+
+func ExampleTanh() {
+	fmt.Printf("%.2f", math.Tanh(0))
+	// Output: 0.00
+}
+
 func ExampleSqrt() {
 	const (
 		a = 3