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Class 10 › Mathematics › Introduction to Trigonometry
CBSE2026Class Class 10 · Mathematics1 Marks · Mcq✅ Verified
Given that $\sin\theta = \frac{a}{b}$, then $\cos\theta$ is equal to:
A. $\frac{b}{\sqrt{b^2-a^2}}$
B. $\frac{b}{a}$
C. $\frac{\sqrt{b^2-a^2}}{b}$
D. $\frac{a}{\sqrt{b^2-a^2}}$
✅ Answer & Solution
✅ Correct Answer: C
In a right triangle, if $\sin\theta = \frac{a}{b}$ (opposite/hypotenuse), then the adjacent side $= \sqrt{b^2-a^2}$ (by Pythagoras). So $\cos\theta = \frac{\text{adjacent}}{\text{hypotenuse}} = \frac{\sqrt{b^2-a^2}}{b}$.
