cos9x cos8x + sin9x sin8x = -1

[TAF]

I seriously need help with this problem. The directions require me to solve for the exact values of x, where 0 < x < 2 pi and x can be all real numbers:

. . .cos9x cos8x + sin9x sin8x = -1

 

[stapel]

The directions require me to solve for the exact values of x, where 0 < x < 2 pi and x can be all real numbers...

Which one? Are you supposed to solve for x between 0 and 2pi, or for all real-valued solutions?

cos9x cos8x + sin9x sin8x = -1

Hint: Review the angle sum and angle difference identities you've been memorizing. The left-hand side fits very neatly into one of them.

Eliz.

 

[TAF]

Thats all the directions said I am guessing its all the ones between 0 and 2 pi

 

[TAF]

Thanks for the help