Cos(90°) = 0
Cosine — the x-coordinate of the corresponding unit-circle point, or adjacent/hypotenuse in a right triangle.
How to derive cos(90°)
At 90° the unit-circle point is (0, 1). Cosine is the x-coordinate, so cos(90°) = 0. This is also why tan(90°) is undefined — the denominator vanishes.
Unit-circle context
The angle 90° corresponds to π/2 radians and sits on an axis on the unit circle.
Other trig values at 90°
Related cos values
Frequently asked
- What is the exact value of cos(90°)?
- The exact value is 0. Its decimal approximation is 0.
- How do you derive cos(90°)?
- At 90° the unit-circle point is (0, 1). Cosine is the x-coordinate, so cos(90°) = 0. This is also why tan(90°) is undefined — the denominator vanishes.
- What is 90° in radians?
- 90° equals π/2 radians (multiply degrees by π/180).
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