Feat/cos (TheAlgorithms#475)

* feat: bitwise min * fix: bitwise min, change for vararg * fix: change min tests * fix: benchmark for bitwise * fix: rename tests * fix: add value param * fix: change condition * feat: added description to some functions * Updated Documentation in README.md * fix: change descriptions * Updated Documentation in README.md * Updated Documentation in README.md * Updated Documentation in README.md * feat: abs algo * Updated Documentation in README.md * fix: add comment * Updated Documentation in README.md * fix: new comment * Updated Documentation in README.md * fix: rename func and remove package * Updated Documentation in README.md * Update math/abs.go Co-authored-by: Taj <[email protected]> * Updated Documentation in README.md * Update math/binary/abs.go Co-authored-by: Taj <[email protected]> * Updated Documentation in README.md * fix: rename func and move binary test * add package description and add function name to comment * Updated Documentation in README.md * rename Intercept method to YIntercept * Updated Documentation in README.md * fix strings * Updated Documentation in README.md * fix commit * added Cosine function * Updated Documentation in README.md * fix after review * Updated Documentation in README.md * fixes * fix: doc comment Co-authored-by: Rak Laptudirm <[email protected]> Co-authored-by: github-action <${GITHUB_ACTOR}@users.noreply.github.com> Co-authored-by: Taj <[email protected]>
pengchant · Mar 20, 2022 · 096521a · 096521a
1 parent 3c64010
commit 096521a
Show file tree

Hide file tree

Showing 3 changed files with 67 additions and 4 deletions.
diff --git a/README.md b/README.md
@@ -548,10 +548,11 @@ Read our [Contribution Guidelines](CONTRIBUTING.md) before you contribute.
 ##### Functions:
 
 1. [`Abs`](./math/abs.go#L11):  Abs returns absolute value
-2. [`FindKthMax`](./math/kthnumber.go#L11):  FindKthMax returns the kth large element given an integer slice with nil `error` if found and returns -1 with `error` `search.ErrNotFound` if not found. NOTE: The `nums` slice gets mutated in the process.
-3. [`FindKthMin`](./math/kthnumber.go#L19):  FindKthMin returns kth small element given an integer slice with nil `error` if found and returns -1 with `error` `search.ErrNotFound` if not found. NOTE: The `nums` slice gets mutated in the process.
-4. [`IsPowOfTwoUseLog`](./math/checkisnumberpoweroftwo.go#L10):  IsPowOfTwoUseLog This function checks if a number is a power of two using the logarithm. The limiting degree can be from 0 to 63. See alternatives in the binary package.
-5. [`Phi`](./math/eulertotient.go#L5):  Phi is the Euler totient function. This function computes the number of numbers less then n that are coprime with n.
+2. [`Cos`](./math/cos.go#L10):  Cos  returns the cosine of the radian argument x. [See more](https://en.wikipedia.org/wiki/Sine_and_cosine) [Based on the idea of Bhaskara approximation of cos(x)](https://math.stackexchange.com/questions/3886552/bhaskara-approximation-of-cosx)
+3. [`FindKthMax`](./math/kthnumber.go#L11):  FindKthMax returns the kth large element given an integer slice with nil `error` if found and returns -1 with `error` `search.ErrNotFound` if not found. NOTE: The `nums` slice gets mutated in the process.
+4. [`FindKthMin`](./math/kthnumber.go#L19):  FindKthMin returns kth small element given an integer slice with nil `error` if found and returns -1 with `error` `search.ErrNotFound` if not found. NOTE: The `nums` slice gets mutated in the process.
+5. [`IsPowOfTwoUseLog`](./math/checkisnumberpoweroftwo.go#L10):  IsPowOfTwoUseLog This function checks if a number is a power of two using the logarithm. The limiting degree can be from 0 to 63. See alternatives in the binary package.
+6. [`Phi`](./math/eulertotient.go#L5):  Phi is the Euler totient function. This function computes the number of numbers less then n that are coprime with n.
 
 ---
 </details><details>

diff --git a/math/cos.go b/math/cos.go
@@ -0,0 +1,17 @@
+// author(s) [red_byte](https://github.com/i-redbyte)
+// see cos_test.go
+
+package math
+
+import "math"
+
+// Cos  returns the cosine of the radian argument x. [See more](https://en.wikipedia.org/wiki/Sine_and_cosine)
+// [Based on the idea of Bhaskara approximation of cos(x)](https://math.stackexchange.com/questions/3886552/bhaskara-approximation-of-cosx)
+func Cos(x float64) float64 {
+	tp := 1.0 / (2.0 * math.Pi)
+	x *= tp
+	x -= 0.25 + math.Floor(x+0.25)
+	x *= 16.0 * (math.Abs(x) - 0.5)
+	x += 0.225 * x * (math.Abs(x) - 1.0) //Extra precision
+	return x
+}
diff --git a/math/cos_test.go b/math/cos_test.go
@@ -0,0 +1,45 @@
+package math
+
+import (
+	"math"
+	"testing"
+)
+
+const epsilon = 0.001
+
+func TestCos(t *testing.T) {
+	tests := []struct {
+		name string
+		n    float64
+		want float64
+	}{
+		{"cos(0)", 0, 1},
+		{"cos(90)", 90, -0.447},
+		{"cos(180)", 180, -0.598},
+		{"cos(1)", 1, 0.540},
+		{"cos(1)", math.Pi, -1},
+		{"cos(1)", math.Pi / 2, 0},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got := Cos(test.n)
+			if math.Abs(got-test.want) >= epsilon {
+				t.Errorf("Cos() = %v, want %v", got, test.want)
+				t.Errorf("MATH Cos() = %v", math.Cos(test.n))
+			}
+		})
+	}
+}
+
+func BenchmarkCos(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Cos(180)
+	}
+}
+
+// BenchmarkMathCos is slower because the standard library `math.Cos` calculates a more accurate value.
+func BenchmarkMathCos(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		math.Cos(180)
+	}
+}