Question

If $\sin a+{\sin }^{2}a=1$, then what will be ${\cos }^{2}a+{\cos }^{4}a$?

Answer 1

$\sin a+{\sin }^{2}a=1$
$⟹\sin a=1-{\sin }^{2}a$
$⟹\sin a={\cos }^{2}a$
$⟹{\sin }^{2}a={\cos }^{4}a$
$⟹1-{\cos }^{2}a={\cos }^{4}a$
$⟹{\cos }^{2}a+{\cos }^4=1$