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Calculate the cosine of any angle in degrees or radians. Cosine represents the x-coordinate on the unit circle.
| Degrees | Radians | Exact Value | Decimal |
|---|---|---|---|
| 0° | 0 | 1 | 1.0000 |
| 30° | π/6 | √3/2 | 0.8660 |
| 45° | π/4 | √2/2 | 0.7071 |
| 60° | π/3 | 1/2 | 0.5000 |
| 90° | π/2 | 0 | 0.0000 |
| 120° | 2π/3 | -1/2 | -0.5000 |
| 135° | 3π/4 | -√2/2 | -0.7071 |
| 150° | 5π/6 | -√3/2 | -0.8660 |
| 180° | π | -1 | -1.0000 |
| 270° | 3π/2 | 0 | -0.0000 |
| 360° | 2π | 1 | 1.0000 |
Domain: All real numbers (-∞, ∞)
Range: [-1, 1]
Period: 2π radians (360°)
cos(θ + 2π) = cos(θ)
Even function: cos(-θ) = cos(θ)
y-axis symmetry
Zeros: 90°, 270°, ...
Max: 0°, 360° | Min: 180°
Cosine is a trigonometric function that returns the x-coordinate of a point on the unit circle. In a right triangle, cos(θ) = adjacent/hypotenuse.
Because cos(-θ) = cos(θ). Negating the angle reflects the point across the x-axis, which doesn't change the x-coordinate.
Cosine is positive in Quadrants I and IV (0° to 90°, 270° to 360°), and negative in Quadrants II and III (90° to 270°).