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Mathematics · 2025 · 1 mark
CBSE 2025 · Region 5 · Set 1 · Q19
Assertion (A): For an acute angle θ, sin θ=3/5 ⇒ cos θ=-4/5. Reason (R): For any value of θ, (0^° ≤ θ ≤ 90^°) sin^2 θ+ cos^2 θ=1.
Assertion (A) : For an acute angle $\displaystyle \theta, \sin \theta=\frac{3}{5} \Rightarrow \cos \theta=-\frac{4}{5}$.
Reason (R) : For any value of $\displaystyle \theta$, $\displaystyle \left(0^{\circ} \leq \theta \leq 90^{\circ}\right)$ \[\sin ^{2} \theta+\cos ^{2} \theta=1 . \]
Official answer
(D)
Assertion (A) is false, but Reason (R) is true.
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CBSE Class 10 Mathematics past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.