I posted this question and learned it from SDN member a week ago.
1. you can solve it by using a sign graph, or just memorize it sin(pie+x) = -sin x
sin(2pie +x) = sin x, Cos(x+2π😉 = cosx,, Cos (x+π😉 = -cosx
I recommend you to understand the graph, so you don't need to memorize it.
2. use the double equation 2sin(pi+x) + sin(x) +2?
for get about 2 at this time just solve sin (pie +x) = sinpie*cosx +sinx*cospie,
sin pie = 0, so you have sinx*cos pie = -sinx
now put 2 back on > -2sinx
so -2sinx +sinx = -sin x , sin x is between [-1, 1], so -(-1)+2 = 3
