showed that $x^2 + y^2$ = $1$ if ........... Please help me .how can I solve this problem:
If $x \sin^3 \alpha$ + $y \cos^3 \alpha$ = $\sin\alpha\cos\alpha$          and            $x \sin\alpha-y\cos\alpha$ = $0$  then showed that $x^2 + y^2$ = $1$

from the second equation, you get $y = x\tan \alpha$
Substitute this in first equation and you will get $x = \cos \alpha$
which means $y= \sin \alpha$
$$x^2+y^2 = \sin^2 \alpha + \cos^2 \alpha = 1$$
proved
