Question

Cos2 П/8-1 sin2 П/8
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Answer 1

$\displaystyle\bf\\\frac{Cos^{2}\frac{\pi }{8} }{1-Sin^{2}\frac{\pi }{8}} =\frac{Cos^{2}\frac{\pi }{8} }{Cos^{2} \frac{\pi }{8} }=1$