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math.atan

trigonometry

The arc tangent of a value. It takes any real number and returns an angle in radians in (-π/2, π/2).

Syntax

math.atan(x)

atan only sees the ratio y/x, so the quadrant is lost: the points (1, 1) and (-1, -1) give the same ratio but angles that differ by π. To get the direction of a vector use math.atan2(y, x) instead — it keeps the quadrant and survives x == 0, where math.atan(y/x) would raise ZeroDivisionError.

Examples

import math
print(math.atan(0))    # → 0.0
print(math.atan(1))    # → 0.7853... (π/4)
print(math.atan(-1))   # → -0.7853...
print(math.atan(math.inf))  # → 1.5707... (π/2)
print(math.degrees(math.atan(1)))  # → 45.0
print(math.atan(0.5))  # → 0.4636...

See also

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