Question

Prove that :

cos theta sin (90° + theta) + sin theta cos (90° - theta) = 1​

Answer 1

Step-by-step explanation:

sin(90+theta)=cos theta

cos(90-theta)=sin theta

by using the formulas

cos theta*cos theta + sin theta*sin theta

cos^2theta+sin^2theta

1

Answer 2

Step-by-step explanation:

sin (90+¢) = cos ¢

cos (90-¢)= sin ¢

cos ¢ sin (90+¢) + sin¢ cos (90-¢)= cos^2¢ + sin^2¢= 1