Question

Sin(pi/4 - α) , если sinα= √2/3 и pi/2<α

Answer 1

$cos alpha =- sqrt{1- frac{2}{9} }=- frac{ sqrt{7} }{3} \sin( frac{ pi }{4} - alpha )=sinfrac{ pi }{4}cos alpha -sin alpha cosfrac{ pi }{4}= frac{ sqrt{2} }{2} (cos alpha -sin alpha )=\= -frac{ sqrt{2} }{6} (sqrt{7} + sqrt{2} )$