(2+sin a)×(2-sin a)+(2+cos a)×(2-cos a)=7

Question

(2+sin a)×(2-sin a)+(2+cos a)×(2-cos a)=7

Answer 1

(2+sina)(2-sina)+(2+cosa)(2-cosa)=7
4-sin²a+4-cos²a=7
-(sin²a+cos²a)+8=7
-1+8=7
7=7