Question

алгебра 10.
как решать...​

Answer 1

Объяснение:

$\frac{sin40\cdot cos20+sin20\cdot sin50}{cos25\cdot cos20-cos70\cdot cos65}=\frac{sin40\cdot cos20+sin20\cdot cos40}{cos25\cdot cos20-sin20\cdot sin25}=\\\\=\frac{sin(40+20)}{cos(25+20)}=\frac{sin60}{cos45}=\frac{\frac{\sqrt3}{2}}{\frac{\sqrt2}{2}}=\frac{\sqrt3}{\sqrt2}=\sqrt{1,5}\\\\\\\star \; \; sina=cos(90^\circ -a)\; \; \; ,\; \; \; cosa=sin(90^\circ -a)\; \; \star$