所有点向右平移π/10个单位,即x本身减去π/10,y=sin(2(x-π/10)-π/5)=sin(2x-2π/5)
横坐标缩短为原来一半,即x系数变为原来二倍y=sin(4x-2π/5)
纵坐标伸长为原来的四倍,即右端的式子乘以四y=4sin(4x-2π/5)