Trig problem with understanding sine, cosine.

Jan 2020
New Jersey
I'm studying trig for fun, and I'm confused about the definition of sine and cosine for a right triangle. I'm using multiple resources that confuse me in the same way. They say the sine of an angle is the ratio of the opposite leg to the hypotenuse. But then they will say that the opposite leg IS the sine of the angle. I can understand how this would be true in regards to a unit circle where the hypotenuse is 1, but for any other hypotenuse values this won't be true?


Math Team
Sep 2015
It's only true if the hypotenuse has length one, i.e. the unit circle.

Your understanding is correct.