Explanation:
STEP 1:
Find a length of third side.
Use the Pythagorean theorem:

STEP 2:
Use the trigonometric functions:

STEP 3:
Use theorem: the sum of the measures of acute angles of the right triangle is 90°.
Example:
We have the length of legs: a = 3, b = 4.
Let c = hypotenuse.
Use the Pyhagorean theorem:

Angle between a and c (β):
Use sine. Therefore b = opposite, c = hypotenuse:

look at the picture

subtract 37° from both sides
