To make a puzzle, Denzel draws lines a and b to cut along on a
square piece of posterboard. He wants to draw line c so that it is
parallel to line b.
What should the
measure of 21 be?
Explain.

Hello! i hope this
since the cosine is the ratio of the adjacent side to the hypotenuse, you can see that cos 60° = ½. answer. according to the property of cofunctions (topic 3), sin 30° is equal to cos 60°. sin 30° = ½.