When a triangle has two angles and a side opposite one of them, the law of sines finds the rest: a/sin A = b/sin B. These free printable worksheets state each triangle and ask for the side marked b, rounded to one decimal place.
If they get stuck
The answer key prints on a separate page.
The law says the ratio of a side to the sine of its opposite angle is the same for all three sides, so one known pair pins down any other side. The parts are named in the sentence — triangle ABC with sides a, b, c opposite the angles A, B, C — the same lettering the formula is written in.
It is a calculator worksheet and prints for that reason: sin 50° comes from a calculator and the answer is an irrational number rounded off. A length is asked to one decimal place, the answer key gives the rounded value, and the step-by-step walk substitutes into the formula before evaluating.
One question from a sheet like this one, worked a step at a time — with a sentence saying what just happened and why.
Law of sines, step by step