Question

ВЫЧИСЛИТЕ ПОЖАЛУЙСТА

Answer 1

$cos54аcos 6а-sin 54аsin6а=cos(54а+6а)=cos 60а= frac{1}{2}$

$cos frac{3pi}{10} cos frac{pi}{20}+sinfrac{pi}{20}sinfrac{3pi}{10}=cos(frac{3pi}{10}-frac{pi}{20})=cos frac{5pi}{20}= frac{sqrt{2}}{2}$

$frac{sin 13аcos 47а+sin47аcos13а}{cos 98аcos38а+sin98аsin38а} = frac{sin(47а+13а)}{cos(98а-38а)} = frac{sin60а}{cos60а} = sqrt{3}$