Question

plz help with this problem I need to find the length of CB???

Answer 1

CB is equal to 10m  you can tell this bye the side DC being 20 m and the angle of DC is half of CB so that means that CB has to be 10 m

Answer 2

$tan(30)=0.57735026919 \\ 0.57735026919= \frac{x}{20}$
Multiply by 20 on both sides
$0.57735026919*20= \frac{x}{20} *20 \\ 11.5470053838=x \\ 11.5=x$
and x = side CA
Next you now know the hypotenuse of the other "triangle"
It's Adjacent and hypotenuse
So that's cos
$cos(60)= \frac{x}{11.5} \\ 0.5= \frac{x}{11.5}$
multiply by 11.5 on both sides
$0.5*11.5= \frac{x}{11.5} * 11.5 \\ 5.75 = x$
x= side CB
CB=5.75m