대답:
아래 참조
설명:
LHS = 왼손 쪽, RHS = 오른손 쪽
LHS =# (sin (2x + x)) / (1 + 2cos2x) #
# = (sin2xcosx + cos2xsinx) / (1 + 2cos2x) #
# = ((2sinxcosx) cosx + (1-2sin ^ 2x) sinx) / (1 + 2cos2x) #
# = (2sinxcos ^ 2x + sinx-2sin ^ 3x) / (1 + 2 (1-2sin ^ 2x)) #
# = (2sinx (1-sin ^ 2x) + sinx-2sin ^ 3x) / (1 + 2-4sin ^ 2x) #
# = (2sinx-2sin ^ 3x + sinx-2sin ^ 3x) / (3-4sin ^ 2x) #
# = (3sinx-4sin ^ 3x) / (3-4sin ^ 2x) #
# = (sinx (3-4sin ^ 2x)) / (3-4sin ^ 2x) #
# = sinx #
# = RHS #
