27 Find the exact value of the given expression using a sum

27. Find the exact value of the given expression using a sum or difference formula. 111t cos A) V3 +1 T2V2 B) 2v2 CO V3-1 2V2 D) 3-1 2V2

Solution

Cos(A +B ) = cos A cosB - sinA sinB

Cos(11/12) = cos(2/3+/4)

Cos(2/3)cos(/4)-sin(2/3)sin(/4)

-1/2(1/2) +(-3/2)(1/2)

(-1-3)/22

Correct option D

Thank you