Definition
A trigonometric function of an angle in a right triangle, equal to the length of the side adjacent to the angle divided by the length of the side opposite the angle. It is the reciprocal of the tangent function.
Plain English
For an angle in a right triangle, the cotangent is the adjacent side divided by the opposite side. It is simply the tangent flipped upside down.
Context Anchor
Seen in aviation math, navigation, and geometry problems that use angles and right triangles.
Derivation
From 'co-' (meaning complementary) and 'tangent.' The cotangent of an angle equals the tangent of its complementary angle (the angle that, added to it, makes 90 degrees). Knowing this helps explain the 'co-' prefix and why the function is paired with tangent.
Why Pilots Care
Pilots rarely use cotangent directly in the cockpit, but it can appear in aviation formulas, training texts, and navigation math. Knowing what it means prevents the formula from turning into meaningless symbols.
Grounding Statement
If you can picture a right triangle, cotangent tells you how long the side beside the angle is compared with the side across from the angle.
Example Sentence 1
When working through a navigation triangle, the cotangent of the angle gives the ratio of the adjacent leg to the opposite leg.
Example Sentence 2
Using the cotangent function helped solve the right-triangle distance problem on the chart.