Consider a similar right triangle AB'C' with a hypotenuse of arbitrary length. Since the triangles are similar, the ratio BC to AB equals the ratio B'C' to AB'. But AB equals 1. The standard notation for a right triangle For a while we'll be looking mainly at right triangles, so it would be useful to use a standard notation for the angles and sides of these triangles. Next we'll look at cosines.
Cosines are just sines of the complementary angle.
For triangle ABC above, cos A is just sin B. Exercises 28. Find a, the side opposite A, and find b, the remaining side. Find c and a. 191. The top of a ladder 50 feet long rests against a building 43 feet from the ground. Next use the Pythagorean theorem to find b knowing a and c. 44.