令cosφ=12/13，sinφ=5/13则原式=13[sin(2x+π/6)cosφ+cos(2x+π/6)sinφ]=13sin(2x+π/6+φ)
用两角和公式：=13sin[2x+π/6+arcsin(5/13)]或者=13sin(2x+π/6+φ) (sinφ=5/13)
