Jika tan x = 1/2, maka 2 sin x + (sin x + phi/2) + cos (phi - x) adalah.... a.akar 5/5 b.1 c.2 akar 5/5 d.3/5 akar 5 e.9/5 akar 5

tan x = 1/2.
r^2 = 1^2 + 2^2
r^2 = 1 + 4
r^2 = 5
r = V5
sin x = 1/V5
cos x = 2/V5
2 sin x + sin (x + phi/2) + cos (phi -x)
= 2 sin x + (sin x cos phi/2 + cos x .sin.phi/2) + (cos phi cos x + sin phi sin x)
= 2 sin x + ( sin x.0 + cos x .1) + (-1.cos x + 0.sin.x)
=2sin x + cos x - cos x
= 2 sin x
= 2(1/V5)
= 2/V5
= (2/5)V5....(c)