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8. Introduction to Trigonometry
medium
જો $\tan 7 \theta \cdot \tan 3 \theta=1,$ હોય તો $\theta$ મેળવો.
A
$30$
B
$18$
C
$15$
D
$9$
Solution
$\tan 7 \theta \cdot \tan 3 \theta=1$
$\therefore \tan 7 \theta=\frac{1}{\tan 3 \theta}$
$\therefore \tan 7 \theta=\cot 3 \theta$
$\therefore \tan 7 \theta=\tan (90-3 \theta)$
$\therefore 7 \theta=90-3 \theta$
$\therefore 10 \theta=90 \quad \therefore \theta=9$
Standard 10
Mathematics
