Question

please help me as soon as possible. ​

Answer 1

$answer$

$lhs = (sec \: a - \cos\: b)(sec \: a + cos \\ a) \\ = sec {}^{2} \: a - \: cos \: {}^{2} \: a \\ = (1 + tan {}^{2} \: a) - (1 - sin {}^{2} a) \\ = sin {}^{2} \:a \: + tan {}^{2} a = rhs$

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Answer 2

Step-by-step explanation:

=sec2A-cos2A [a2-b2=(a+b)(a-b)]

=1+ten2A-cos2A (sec2=1+ten2)

=sin2A+ten2A (1-cos2=sin2)