1.

A rectangle is inscribed in a semi-circle of radius `r` with one of its sides on diameter of semi-circle. Find the dimensions of rectangle so that the area is maximum. Find the area also.

Answer» `A(theta)=widthxxheight`
`=(2rcostheta)xxrsintheta`
`=2r^2sinthetacostheta`
`=r2xx(2sinthetacostheta)`
`=sin2theta`
`A(theta)=x^2xxsin(2theta)`
`sin(2theta)=1`
`2theta=pi/4`
`theta=pi/4`
Maximum area = `r^2xx1=r^2`
`width=2xcostheta=2rcospi/4`
`=2rxx1/sqrt2`
`=sqrt2r`
`height =rsintheta=rxxsin(pi/4)`
`=r/sqrt2`


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