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What is cot 0 on the unit circle?

Published in Trigonometry 1 min read

Cot 0 is undefined on the unit circle.

To understand why, let's break down the concept. Cotangent (cot) is defined as the ratio of the adjacent side to the opposite side in a right triangle, or equivalently, as x/y on the unit circle, where (x, y) are the coordinates of a point on the unit circle corresponding to the angle. Cotangent can also be expressed as cos(θ)/sin(θ).

When the angle is 0 degrees, the corresponding point on the unit circle is (1, 0).

Therefore:

  • x = 1
  • y = 0

cot(0) = x/y = 1/0

Division by zero is undefined in mathematics. Alternatively, cot(0) = cos(0)/sin(0) = 1/0, which is also undefined. As the angle approaches 0, the value of cotangent approaches infinity (either positive or negative depending on the direction of approach).

Therefore, cot 0 is undefined or can be said to approach infinity.

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