Definition
The two sides of a right triangle that form the 90-degree angle. The third side, opposite the right angle, is called the hypotenuse and is not a leg.
Plain English
The two shorter sides of a right triangle that meet at the square corner. The slanted side across from that corner is not one of the legs.
Context Anchor
Seen in pilot math, navigation problems, wind triangles, and climb or descent calculations that use a right triangle.
Derivation
From the Latin triangulum, meaning 'three-cornered.' A 'right' triangle is one containing a right angle (90 degrees). The two sides forming that square corner are called legs because they 'stand' the triangle up like the legs of a stool.
Why Pilots Care
Pilots apply this concept to break down wind, speed, and course vectors into usable components during flight planning.
Grounding Statement
Picture an L shape: the two strokes of the L are the legs, and the diagonal line closing the triangle is the side across from the square corner.
Intuition Check
Do not confuse legs of a right triangle with flight legs on a route. Here, legs means the two sides that form the 90-degree angle.
Example Sentence 1
When solving a wind triangle, the headwind and crosswind components form the two legs of a right triangle, and the total wind is the hypotenuse.
Example Sentence 2
In the wind triangle solution, the north-south and east-west distances formed the legs.