Explanation
$$dx=a\sin \theta.d\theta$$ $$dy=a\cos \theta.d\theta$$ Or $$\dfrac{-dx}{dy}=-\tan\theta$$. Thus Equation of normal will be $$y-a\sin \theta=-\tan\theta(x-a+a\cos \theta)$$ Or $$\cos \theta.y-a\sin \theta.\cos \theta=-x\sin \theta+a\sin \theta-a\sin \theta \cos \theta$$ $$\cos \theta.y+\sin \theta.x=a\sin \theta$$ Hence it passes through the fixed point $$(a,0)$$.
$$dx=a(-\sin \theta+\theta.\cos \theta+\sin \theta).d\theta$$ $$dx=a(\theta.\cos \theta)$$ $$dy=a(\theta.\sin \theta)d\theta$$. Hence $$\dfrac{-dx}{dy}=-\cot\theta.$$ $$=\tan(\dfrac{\pi}{2}+\theta)$$ Hence it makes an angle of $$\dfrac{\pi}{2}+\theta$$ with the x axis. Now equation of normal $$y-a\sin \theta+a\theta.\cos \theta=-\cot\theta(x-a\cos \theta-\theta \sin \theta).$$ Hence $$\sin \theta y-a\sin ^{2}\theta+a\theta.\cos \theta.\sin \theta=-x\cos \theta+a\cos ^{2}\theta+a\theta.\sin \theta.\cos \theta$$ $$y.\sin \theta+x\cos \theta=a$$ Hence Distance from origin is '$$a$$'.
Let $$x=a\sqrt{\cos \theta}$$ $$y=a\sqrt{\sin \theta}$$ Hence $$\dfrac{dy}{dx}$$ $$=-\dfrac{\cos \theta.\sqrt{\cos \theta}}{\sin \theta.\sqrt{\sin \theta}}$$ $$=\cot\theta^{\dfrac{3}{2}}$$. Hence equation of tangent will be $$y-a\sqrt{\sin \theta}=-\dfrac{\cos \theta.\sqrt{\cos \theta}}{\sin \theta.\sqrt{\sin \theta}}(x-a\sqrt{\cos \theta})$$ $$\sin \theta.\sqrt{\sin \theta}y-a\sin ^{2}\theta=-\cos \theta\sqrt{\cos \theta}x+a\cos ^{2}\theta$$ $$(\sin \theta)^{\dfrac{3}{2}}.y+(\cos \theta)^{\dfrac{3}{2}}x=a$$ Hence the intercepts are $$Q=\dfrac{a}{(\sin \theta)^{\dfrac{3}{2}}}$$ and $$P=\dfrac{a}{(\cos \theta)^{\dfrac{3}{2}}}$$ Hence $$Q^{\dfrac{-4}{3}}+P^{\dfrac{-4}{3}}$$ $$=a^{-\dfrac{4}{3}}[\cos ^{2}\theta+\sin ^{2}\theta]$$ $$=a^{-\dfrac{4}{3}}$$.
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