因为sin1=sin(180/π) sin2=(2*180/π)
180/π < π/3 π/32< 2*180/π < 2π/3
又sin2π/3>sinπ/3
所以sin2>sin1
又π/32< 2*180/π < 2π/3
所以cos2cos2
sin4=sin(4*180/π)
πcos(-13π/10)
①正确