8. Introduction to Trigonometry
medium

જો $\sin 5 \theta=\cos 5 \theta,$ તો $\theta$ મેળવો.

A

$10$

B

$9$

C

$18$

D

$15$

Solution

$\sin 5 \theta=\cos 5 \theta$

$\therefore \sin 5 \theta=\sin (90-5 \theta) \, \therefore 5 \theta=90-5 \theta \, \therefore 10 \theta=90\, \therefore \theta=9$

OR

$\sin 5 \theta=\cos 5 \theta $.      But $\sin 45=\cos 45$    $ \therefore 5 \theta=45 $    $ \therefore \theta=9$

Standard 10
Mathematics

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