Answer:
D. 1/2
Step-by-step explanation:
Because if you choose A , you get +4
if you choose B ,you get -12
Choose C , you get +20
D is the correct answer.
Because they are math buddies say 2x2=4. You can divide 4÷2 and get your original factor (2)... Sorry if it's wrong I think that's what it means ,hope it helps!
Using cos addition formula:
use x for theta
cos(x+π/6)=cosx*cos(π/6)-sinx*sin(π/6)
sinx=1/4
cosx=√15/4
cos(π/6)=√3/2
sin(π/6)=1/2
cos(x+π/6)=(√15/4*√3/2)-(1/4*1/2)
cos(x+π/6)=(√45/8)-(1/8 )
cos(x+π/6)=(√45-1)/8)