X-2y3 how do u simplify that

Express the following as a function of a single angle, cos(60) cos(-20) - sin(60) sin(-20)

The radical equation 2+√2x-3 = √x+7 has a solution set [x= a0} and an extraneous root x = a1.

40 points. given: two congruent angles ∠c and ∠r are supplementary. prove: ∠r and ∠c are both right angles. it doesn't have to be exactly 10 rows.statements reasons1. 1. 2. 2. 3. 3. 4. 4. 5. 5. 6. 6. 7. 7. 8. 8. 9. 9. 10. 10.