True or false? a theorem is a statement that can be easily proved using a corollary

Which of the following is the result of expanding

1. 2. ∠b and ∠y are right angles. 3.? 4.? which two statements are missing in steps 3 and 4? ∠x ≅ ∠c △abc ~ △zyx by the sas similarity theorem. ∠b ≅ ∠y △abc ~ △zyx by the sas similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem. = 2 △abc ~ △zyx by the sss similarity theorem.

Find the area of the region that is inside r=3cos(theta) and outside r=2-cos(theta). sketch the curves.