Question

помогите дам 50балов
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Answer 1

$\displaystyle\bf\\Ctg\alpha =-2\\\\Ctg^{2}\alpha =4 \\\\1+Ctg^{2}\alpha = \frac{1}{Sin^{2}\alpha }\\\\Sin^{2} \alpha =\frac{1}{1+Ctg^{2} \alpha } =\frac{1}{1+4}=\frac{1}{5}=0,2\\\\\\ Sin^{4} \frac{\alpha }{2} +Cos^{4} \frac{\alpha }{2}=\Big(\underbrace{Sin^{2} \frac{\alpha }{2} +Cos^{2} \frac{\alpha }{2}}_{1}\Big)^{2} -2Sin^{2} \frac{\alpha }{2} Cos^{2} \frac{\alpha }{2} =\\\\\\=1-\frac{1}{2}\cdot 4 Sin^{2} \frac{\alpha }{2} Cos^{2} \frac{\alpha }{2}=1-0,5Sin^{2} \alpha =1-0,5\cdot 0,2=0,9$