A = 2(sina*cosb+cosa*sinb)(cosa*cosb+sina*sinb) A = 2[(sina*cosb)(cosa*cosb)+(sina*cosb)(sina*sinb)+(cosa*sinb)(cosa*cosb)+(cosa*sinb)(sina*sinb)A= 2(sina*cosa*cos2b + sin2a*sinb*cosb + cos2a*sinb*cosb + sin2b*sina*cosa)A= sin2a cos2b + sin 2b sin2a + sin2b cos2a + sin2a sin2bA= sin2a+sin2bĐúng thì vote
A = 2(sina*cosb+cosa*sinb)(cosa*cosb+sina*sinb) A = 2[(sina*cosb)(cosa*cosb)+(sina*cosb)(sina*sinb)+(cosa*sinb)(cosa*cosb)+(cosa*sinb)(sina*sinb)A= 2(sina*cosa*cos2b + sin2a*sinb*cosb + cos2a*sinb*cosb + sin2b*sina*cosa)A= sin2a cos2b + sin 2b sin2a + sin2b cos2a + sin2a sin2bA= sin2a+sin2bĐúng thì vote