横坐标缩短为原来的2倍
矛盾啊
伸长为原来的2倍
就相当于x前面的系数除以2
就是y=2sin(x+π/3)
缩短为原来的1/2倍
就相当于x前面的系数乘以2
救赎y=2sin(4x+π/3)
2、
(sinx-3cosx)/(3sinx+cosx)
=(2cosx-3cosx)/(6cosx+cosx)
=-cosx/7cosx
=-1/7
3、
sin2013°
=sin(2013-360)
=sin(2013-360-360)
=……
=sin213°
=sin(180°+33°)
=-sin33°
=-m
4、cos50°cos128°+cos40°cos38°
=-cos50°sin38°+sin50°cos38°
=sin(50°-38°)
=sin12°
5、点是什么
没给全