Two angles that can be trisected with a straightedge and compass are a 90 angle and a _____ angle.A.45B.90C.9D.75SUBMITarrow_backPREVIOUS

To find an angle that can be trisected using just a straightedge and compass, we need to consider the properties of constructible angles. A well-known fact is that specific angles that can be trisected include angles that are multiples of 30 degrees or specific combinations.

Analysis:

1. Trisectable Angles: Angles that can be trisected using a straightedge and compass typically include multiples of 30 degrees (like 30, 60, and 90 degrees).

2. Options Given:

   • A. 45 degrees: Constructible angle (can be trisected to get 15 degrees).
   • B. 90 degrees: Already known as constructible (can be trisected to get 30 degrees).
   • C. 9 degrees: Not constructible using just a straightedge and compass.
   • D. 75 degrees: Not constructible using just a straightedge and compass.

Conclusion:

The only angle from the given options that can be trisected in addition to 90 degrees is 45 degrees.

Final Answer

The angle is A. 45 degrees.