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Mathematics · 2026 · 3 marks
CBSE 2026 · Region 5 · Set 2 · Q31
Prove that: (1+ cot θ- cosec θ)(1+ tan θ+ sec θ)=2
Prove that : $\displaystyle (1+\cot \theta-\operatorname{cosec} \theta)(1+\tan \theta+\sec \theta)=2$
Marking-scheme solution
\[\begin{aligned}
& \text { LHS }=\left(1+\frac{\cos \theta}{\sin \theta}-\frac{1}{\sin \theta}\right)\left(1+\frac{\sin \theta}{\cos \theta}+\frac{1}{\cos \theta}\right) \\
& =\frac{\sin \theta+\cos \theta-1}{\sin \theta} \times \frac{\cos \theta+\sin \theta+1}{\cos \theta} \\
& =\frac{1}{\sin \theta \cos \theta}\left[(\sin \theta+\cos \theta)^{2}-1\right] \\
& =\frac{2 \sin \theta \cos \theta}{\sin \theta \cos \theta}
\end{aligned}
\]
= $\displaystyle 2$ = RHS
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CBSE Class 10 Mathematics past-paper question from the 2026 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.