Question

докажите равновесие

Answer 1

$dfrac{(cos15 beta +cos beta)+cos7 beta }{sin7 beta +(sin15 beta -sin beta)} = ctg7 beta \ dfrac{2cos8 beta cos 7beta+cos7 beta }{sin7 beta +2cos8 beta sin 7beta} = ctg7 beta \ dfrac{cos7 beta( 2cos 8beta+1) }{sin7 beta( 2cos 8beta+1)} = ctg7 beta$
$dfrac{cos7 beta }{sin7 beta} = ctg7 beta \ ctg7 beta= ctg7 beta$
Доказано.