triangle · (math.) trigonometry

Heron's Formula shows how the area of a triangle can be expressed as a function of its side lengths.

Find the radius of the incircle of the triangle.

Hey, sir, the function on the blackboard is not exponential, but trigonometric.

She likes wearing boxer briefs, she doesn't like briefs, and also doesn't like thongs.

The trigonometric functions satisfy a wide array of notable algebraic identities.