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8. Introduction to Trigonometry
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જો $\sec 4 A =\operatorname{cosec}( A -20),$ કે જ્યાં $4 A$ એ લઘુકોણમાંથી મેળવેલ છે તો $A=\ldots \ldots \ldots \ldots .$
A
$45$
B
$70$
C
$30$
D
$22$
Solution
$\sec 4 A =\operatorname{cosec}( A -20)$
$\therefore \operatorname{cosec}(90-4 A )=\operatorname{cosec}( A -20)$
$\therefore 90-4 A = A -2 O$
$\therefore 90+20=A+4 A$
$\therefore 5 A=110$
$\therefore A=22$
Standard 10
Mathematics