Anonymous

sin(2x)>0=> 2x is in the 1st or the 2nd quadrant. tan x=0.8=>x=38.6598082...=>2x=77.3196165... Thus sin(2x)=sin(77.3196165..)=0.97561 approximately.

Anonymous

tan x = 4/5 sin x = 3 / √41 cos x = 5 / √41 sin 2x = 2 sin x cos x sin 2x = 2 [ 3 / √41 ] [ 5 / √41 ] sin 2x = 30 / 41