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3.Trigonometrical Ratios, Functions and Identities
easy
$(\sec 2A + 1){\sec ^2}A = $
A
$\sec A$
B
$2\sec A$
C
$\sec 2A$
D
$2\sec 2A$
Solution
(d) $(\sec 2A + 1){\sec ^2}A $
$= \left( {\frac{{1 + {{\tan }^2}A}}{{1 – {{\tan }^2}A}} + 1} \right)\,(1 + {\tan ^2}A)$
$ = \frac{{2\,(1 + {{\tan }^2}A)}}{{1 – {{\tan }^2}A}}$
$= 2\sec 2A.$
Standard 11
Mathematics