Cosine Calculator

How it works

1. 1Enter any angle value and choose whether it is in degrees or radians using the unit tabs.
2. 2The calculator applies cos(θ), snapping floating-point noise so results like cos(90°) return exactly 0.
3. 3The result is the ratio of the adjacent side to the hypotenuse — always a value between −1 and 1.

Use cases

• Physics and engineering: resolving a force vector into its horizontal component using F·cos(θ).
• Computer graphics: computing the dot-product lighting term between a surface normal and a light direction.
• Trigonometry homework: verifying cos values for standard angles such as 0°, 30°, 45°, 60°, and 90°.

Frequently asked questions

What does cosine measure?

Cosine gives the ratio of the adjacent side to the hypotenuse in a right triangle. On the unit circle it equals the x-coordinate of the point at angle θ.

Why does cos(90°) return 0 instead of a tiny decimal?

Floating-point arithmetic produces a residual near 6×10⁻¹⁷ for cos(π/2). The calculator snaps values within 10⁻¹² of zero to exactly 0, matching the true result.

Can cosine ever exceed 1 or −1?

No — for real angles cos(θ) always lies in [−1, 1]. It equals 1 at 0° and −1 at 180°.