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8. Introduction to Trigonometry
easy
Given that $\alpha+\beta=90^{\circ},$ show that
$\sqrt{\cos \alpha \operatorname{cosec} \beta-\cos \alpha \sin \beta}=\sin \alpha$
Option A
Option B
Option C
Option D
Solution
$\sqrt{\cos \alpha \operatorname{cosec} \beta-\cos \alpha \sin \beta}=\sqrt{\cos \alpha \operatorname{cosec}\left(90^{\circ}-\alpha\right)-\cos \alpha \sin \left(90^{\circ}-\alpha\right)}$ $\left[\right.$ Given $\left.\alpha+\beta=90^{\circ}\right]$
$=\sqrt{\cos \alpha \sec \alpha-\cos \alpha \cos \alpha}$
$=\sqrt{1 \cos ^{2}}$
$=\sin \alpha$
Standard 10
Mathematics