1. An isosceles triangle has two equal sides and you have the length of these sides (a=105 feet), but you need the other one: "b". So, if you a draw a segment that bisects the angle of 85.9°,you will obtain two equal right triangles, as you can see in the figure attached. Now, you have to find the value of "x" and the side "b" will be 2x:
Sin(α)=Opposite/Hypotenuse
α=89.5°/2=42.95°
Opposite=x
Hypotenuse=105
Sin(42.95°)=x/105
x=(105)(Sin(42.95°))
x=71.54 feet
2. Then the other side of the isosceles triangle (b), is:
b=2x
b=2x71.54 feet
b=143.08 feet
3. The perimeter of the isosceles triangle, is:
P=2a+b
P=2(105 feet)+143.08 feet
P=210 feet+143.08 feet
P=353 feet
