Question

pomogite reshit etu zadachu

Answer 1

$cos^255-cos^2125=(cos55-cos125)(cos55+cos125)=\\=-2cdot sin90cdot sin(-35)cdot 2cos90cdot cos35=0,; tak; kak; cos90=0$

Answer 2

no eto ne 35 a 55

Answer 3

55+125=180, 125-55=70