0
Using the trigonometric identity cos(a)cos(b) + sin(a)sin(b) = cos(a-b), we can rewrite the given expression as:
cos(81-36) = cos(45) = 0
Therefore, the expression sin(81)sin(36) + cos(81)cos(36) simplifies to 0.
0
Using the trigonometric identity cos(a)cos(b) + sin(a)sin(b) = cos(a-b), we can rewrite the given expression as:
cos(81-36) = cos(45) = 0
Therefore, the expression sin(81)sin(36) + cos(81)cos(36) simplifies to 0.