Question

(sin^2 22,5° - cos ^2 22,5°) ^2=
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Answer 1

$\displaystyle\bf\\\Big(Sin^{2} 22,5^\circ-Cos^{2} 22,5^\circ\Big)^{2} =\Big(Cos^{2} 22,5^\circ-Sin^{2} 22,5^\circ\Big)^{2} =\\\\\\=Cos^{2} \Big(2\cdot 22,5^\circ\Big)=Cos^{2} 45^\circ=\Big(\frac{1}{\sqrt{2} } \Big)^{2} =\frac{1}{2} =0,5$