Two angles that can be trisected with a straightedge and compass are a 90angle and a angle.
a. 9
b. 75
c. 45
d. 90

The correct answer is:

C) 45.

Explanation:

An angle of measure  can be trisected if and only if N is not divisible by 3.

A 45° angle in radians is . Setting up a proportion, we can find the value of N to determine if this fits:



Cross multiply:


 
This means N = 8, and is not divisible by 3; thus the 45 degree angle is trisectible.