Question

If $sinA+si{n}^{2}A=1$, then $co{s}^{2}A+co{s}^{4}A=?$

• A. 0.0
• B. 1
• C. 2
• D. 3

Answer 1

The correct option is B 1

We have,

$sinA+si{n}^{2}A=1$
$\Rightarrow sinA=1-si{n}^{2}A$

$\Rightarrow sinA=co{s}^{2}A---\left(i\right)$

Squaring both sides,

$\Rightarrow si{n}^{2}A=co{s}^{4}A---\left(ii\right)$

From equations (i) and (ii), we have

$co{s}^{2}A+co{s}^{4}A=sinA+si{n}^{2}A=1$