Question

Solve: $si{n}^{4}Acose{c}^{2}A+co{s}^{4}Ase{c}^{2}A=1$

Answer 1

${\sin }^{4}Acose{c}^{2}A+{\cos }^{4}A{\sec }^{2}A=\frac{{\sin }^{4}A}{{\sin }^{2}A}+\frac{{\cos }^{4}A}{{\cos }^{2}A}={\sin }^{2}A+{\cos }^{2}A=1$