Use the triangle formed by the height of the trapezoid to find the lengths of the two sides of the trapezoid and the length of b2:
tan(60)=oppositeadjacent . Adjacent=5tan(60)=2.89 cm.
This finds the base of the triangle, which can be added twice to b1 to find b2: b2=8+2.89+2.89=13.78 cm.
Now, use the same triangle to find the length of the sides.
sin(60)=oppositehypotenuse . Hypotenuse=5sin(60)=5.77 cm.
Lastly, add all of the lengths together: b1+b2+2(l)=8+(2.78+2.78+8)+2(5.77)=33.32 cm.
