यदि `theta - phi=(pi)/(2)` है तो सिध्द कीजिए कि
`[(cos^(2)theta, cos theta,sintheta),(costheta,sintheta,sin^(2)theta)]`
`[(cos^(2)phi,cosphi,sinphi),(cosphi,sinphi,sin^(2)phi)]=0`

Answer

`[:'theta-phi=(pi)/(2)rArrcos(theta-phi)=cos(pi)/(2)=0]`