X = 12
Use the Pythagorean Theorem.
13^2 = 5^2 + x^2
169 = 25 + x^2
Subtract 25 from both sides.
144 = x^2
Take the square root.
12 = x
Divide 296 by 16 you get 18.5 then add the 5.75 to get 24.25
So the answer is 24.25
We will turn the left side into the right side.

Use the identity:



Now use the identity
solved for sin^2 x and for cos^2 x.




You have to find the cos of angle A, so use the Pythagorean equation and trig laws to find the other side of the triangle created by angle A. 3^2 + x^2 = 5^2. x=4. This means cos(A) = 4/5). Make both cos (A) and cos (B) have equal denominators, and add. 148/185 + 60/185 = 208/185. This answer is correct, though it doesn’t appear to be any of the answers you wrote, so either those answers are wrong or you wrote something incorrectly in the problem.