f(x)=(向量a+向量b)*(向量a-向量b)
=a^2-b^2
=[sin(wx+p)]^2+4-{1+[cos(wx+p)]^2}
=3-cos(2wx+2p),
(1)y=f(x)的图像过点M（1,7/2),且相邻对称轴之间的距离为2,w>0,0