Question

срочно надо пжжжжжжжж помогитеее​

Answer 1

$alphain2chetverti Rightarrow Cosalpha<0\\Cosalpha=-sqrt{1-Sin^{2}alpha}=-sqrt{1-0,2^{2}}=-sqrt{1-0,04}=-sqrt{0,96}=-frac{4sqrt{6}}{10}=-frac{2sqrt{6}}{5}\\Sin(frac{pi }{4}-alpha)=Sinfrac{pi }{4}Cosalpha-Cosfrac{pi }{4}Sinalpha=frac{sqrt{2}}{2}*(-frac{2sqrt{6}}{5})-frac{sqrt{2}}{2}*frac{1}{5}=-frac{2sqrt{3}}{5}-frac{sqrt{2}}{10}=-frac{4sqrt{3}+sqrt{2}}{10}$