How do you find the sine, cosine, and tangent of a triangle?

Answer 1

You do not.
Those are functions of an ANGLE, not a triangle

They are defined in a right triangle.
If A is one of the two angles that is not 90 degrees then
sin A = opposite side/hypotenuse
cos A = adjacent side / hypotenuse
tan A = sin A/cos A = opposite/adjacent

Answer 2

Thank you!