Find the value of sin (1/2x) if cos (x)= 1/8

Thxs

cos(x)=1/8
cos(x)=1-2sin^2(1/2x) (that a double angle formula cosK= 1-2sin^29K/2))
sin(1/2x)=sqrt((1-cosx)/2)
=sqrt((1-1/8)/2)
=(sqrt7)/4

sin^2(1/2x)=1/2-12cosx
sin1/2x=1/2-1/8
sin1/2x=3/4