Math & Trig

COS Formula

COS returns the cosine of an angle in radians. Cosine represents the x-coordinate on the unit circle and is used in physics, engineering, signal processing, and geometry. Like SIN, the argument must be in radians — wrap degrees in RADIANS() first.

Syntax

COS(number)
ParameterDescription
number Parameter of the COS function.
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Examples

Cosine of 0

Formula
=COS(0)
Returns 1. The cosine of 0 radians (0°) is 1. Cosine starts at its maximum value.

Cosine of 60 degrees

Formula
=COS(RADIANS(60))
Returns 0.5. The cosine of 60° is exactly 0.5.

Horizontal force component

Formula
=100*COS(RADIANS(30))
Returns ~86.6. A 100-newton force at 30° from horizontal has a horizontal component of 100×cos(30°) ≈ 86.6 newtons.

Common Errors

#VALUE!

Non-numeric arguments return #VALUE!. The input must be a number in radians.

Tips

Force decomposition

In physics, the horizontal component of a force at angle θ is F×COS(θ). The vertical component is F×SIN(θ).

SIN and COS relationship

COS(x) = SIN(x + π/2). They're the same wave shifted by 90°. Also, SIN²(x) + COS²(x) = 1 always.

Radians, not degrees

Like SIN, COS requires radians. COS(180) is NOT -1 (that's 180 radians). Use =COS(RADIANS(180)) to get -1.

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