8. Introduction to Trigonometry
hard

सिद्ध कीजिए कि $\sec A (1-\sin A )( sec A +\tan A )=1$

Option A
Option B
Option C
Option D

Solution

$LHS =\sec A (1-\sin A )(\sec A +\tan A )$

$=\left(\frac{1}{\cos A }\right)(1-\sin A )\left(\frac{1}{\cos A }+\frac{\sin A }{\cos A }\right)$

$=\frac{(1-\sin A)(1+\sin A)}{\cos ^{2} A}=\frac{1-\sin ^{2} A}{\cos ^{2} A}$

$=\frac{\cos ^{2} A}{\cos ^{2} A}=1=R H S$

Standard 10
Mathematics

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