Verified answer

The answer is B. It's just the backwards formula of the cosine addition of angles formula cos(a - b) = cos(a)cos(b) + sin(a)sin(b). in this case a is 65 and b is 50 so the equation can be rewritten as cos(65-50) = cos(15)

Note the formula,

cos(x-y) = cos x cos y + sin x sin y

So, the answer is cos(65° - 50°) = cos(15°) = cos65°cos50° + sin65°sin50°

Choice (B)

The identity is

cos (A - B) = cos A * cos B + sin A * sin B

So cos 65 * cos 50 + sin 65 * sin 50 = cos (65 - 50) = cos 15°

So Answer B is correct

the answer is B , cos15.

how did i get that??

well i found out the value of the expression using a scientific calculator and found the cos inverse of the answer which was 15.

ANSWER IS D