cos^2 ∠ A=1-sin^2 ∠ A=1-(0,2sqrt(21))^2=1-0,84=0,16
cos ∠ A=0,4
tg ∠ A=sin ∠ A/cos ∠ A=sqrt(21)/2
tg ∠ A=CB/AC
CB=AC*tg ∠ A=6sqrt(21)
∠ BCH= ∠ A
sin ∠ BCH=0,2sqrt(21)
sin ∠ BCH=BH/CB
BH=CB*sin∠ BCH=6sqrt(21)*0,2sqrt(21)=[b]25,2[/b]