Question

solve it fast it's urgent​

Answer 1

Answer:

Step-by-step explanation:

as we all know that cos C + cos D = 2cos {(C+D)/2}cos {(C-D)/2}

cos(π/4 +x) + cos (π/4 - x)

= 2cos{(π/4 + x+ π/4 -x)/2} cos {(π/4 + x - π/4 + x)/2}

= 2 cos (π/4) cos (2x/2)

= 2×(1/√2)×cos x

= √2 cosx