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# Java - Math.cos() method example

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The `Math.cos()` function returns the cosine of the specified angle in radians in the range `-1` to `+1`.

``````public class MathExample {

public static void main(String[] args) {
System.out.println( Math.cos( 0                  ) ); //   1 <-     0 degrees
System.out.println( Math.cos( 1.5707963267948966 ) ); //  ~0 <-  ~90 degrees ==  PI / 2
System.out.println( Math.cos( 3.1415926535897932 ) ); // ~-1 <- ~180 degrees ==  PI
System.out.println( Math.cos( 4.71238898038469   ) ); //  ~0 <- ~270 degrees == -PI * (3 / 2)
System.out.println( Math.cos( 6.2831853071795850 ) ); //  ~1 <- ~360 degrees ==  PI * 2

System.out.println( Math.cos(-1.5707963267948966 ) ); //  ~0 <- ~-90 degrees == -PI / 2
}
}``````

Note: `6.123233995736766e-17`, `-1.8369701987210297e-16` and `6.123233995736766e-17` should be equal to `0` but they are not because of computation precision error.

## 1. Documentation

 Syntax ``````package java.lang; public final class Math { public static double cos(double number) { ... } }`````` Note: Classes in the `java.lang` package are imported automatically, so it is not necessary to do it manually - we use just `Math.cos()` call. Parameters `number` - double value in radians (primitive value). Result returns a numeric value between `-1` and `+1`, which represents the cosine of the angle (primitive value). Description `cos` is a static method that takes only one parameter and returns an approximation of `cos(x)` mathematical function result.

``````public class MathExample {

public static void main(String[] args) {
double x1 = 0.0;          // beginning of calculation in radians
double x2 = Math.PI / 2;  // ending of calculation radians

double dx = Math.PI / 9; // calculation step in degrees

}
}
}``````

Output:

``````cos(0.0 rad) = 1.0

## 3. Working with degrees

``````public class MathExample {

static double calculateCos(double deg) {
double rad = (Math.PI / 180) * deg;

}

public static void main(String[] args) {
double x1 = 0.0;  // beginning of calculation in degrees
double x2 = 90.0; // ending of calculation degrees

double dx = 15.0;  // calculation step in degrees

for (double deg = x1; deg  <= x2; deg  += dx) {
double y = calculateCos(deg );

System.out.println("cos(" + deg + " deg) = " + y);
}
}
}``````

Output:

``````cos(0.0 deg) = 1.0
cos(15.0 deg) = 0.9659258262890683
cos(30.0 deg) = 0.8660254037844387
cos(45.0 deg) = 0.7071067811865476
cos(60.0 deg) = 0.5000000000000001
cos(75.0 deg) = 0.25881904510252074
cos(90.0 deg) = 6.123233995736766E-17``````

## 4. Reversed console plot example

``````public class MathExample {

public static void main(String[] args) {
double x1 = 0.0;      // beginning of cosine chart
double x2 = 3 * 3.14; // end of cosine chart

double dx = 3.14 / 4.0; // x axis step
double dy = 1.0  / 5.0; // y axis step

double y1 = 0.0;
double y2 = Math.cos(rad) + 1;

StringBuilder line = new StringBuilder();

for(double y = y1; y < y2; y += dy) {
line.append(" ");
}
System.out.println(line.append("+"));
}
}
}``````

Output:

``````           +
+
+
+
+
+
+
+
+
+
+
+``````

## References

1. Cosine - Wikipedia

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