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8. Introduction to Trigonometry
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$a \sin \theta=3$ અને $a \cos \theta=4,$ તો $a=\ldots \ldots \ldots . . .$ (કે જ્યાં, $a > 0)$
A
$5$
B
$4$
C
$3$
D
$2$
Solution
$a \sin \theta=3 $ $ \therefore a^{2} \sin ^{2} \theta=9$
$a \cos \theta=4$ $\therefore a^{2} \cos ^{2} \theta=16$
$\therefore a^{2} \sin ^{2} \theta+a^{2} \cos ^{2} \theta=9+16$
$\therefore a^{2}\left(\sin ^{2} \theta+\cos ^{2} \theta\right)=25$
$\therefore a^{2}(1)=25$
$\therefore a=5$
Standard 10
Mathematics
