Question

value of 9sec² A-9 tan² A

Answer 1

HEYA!!
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$\\ taking \: 9common \\ \\ \\ 9( \sec {}^{2} a - tan {}^{2} a) \\ \\ now \: use \: the \: identity \: sec {}^{2} a - tan {}^{2} a = > 1 \\ \\ we \: have \: \: \\ \\ 9(1) = 9$
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Answer 2

it is very simple
$9( { \sec(a) }^{2} - { \tan(a) }^{2}) \\ 9(1) = 9$
because sec^2 A-tan^2 A = 1
from identity 2