MCQ
If $\sin \theta=\frac{3}{5}$ then $\cos \theta=?$
- A$\frac{5}{3}$
- B$\frac{3}{5}$
- C$\frac{4}{5}$
- D$\frac{5}{4}$
✓
Answer
$\frac{4}{5}$
$\cos \theta=\sqrt{1-\sin ^2 \theta}$
$\therefore \cos \theta=\sqrt{1-\left(\frac{3}{5}\right)^2}$
$\therefore \cos \theta=\sqrt{1-\left(\frac{9}{25}\right)}$
$\therefore \cos \theta=\sqrt{\frac{16}{25}}$
$\therefore \cos \theta=\frac{4}{5} .$
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