값 영역 y=-2cos^2x+2sinx+3/2,x*8712°[-pi/4,pi/4]

값 영역 y=-2cos^2x+2sinx+3/2,x*8712°[-pi/4,pi/4]

y=-2cos^2x+2sinx+3/2
=-2(1-sin^2x)+2sinx+3/2
=-2sin^2x+2sin^2x-1/2
=-2(sinx-1/2)^2
-π/4