y'=cosx
x=1/2时,
y=sin(1/2),y'=cos(1/2)
则在此点的切线为y=cos(1/2)*(x-1/2)+sin(1/2)已知抛物线y方=4x焦点为 求秒解y²=2px=4x, 得p=2焦点为(p/2,0)，即(1,0)