Two corners of a triangle have angles of (5 pi )/ 8 and ( pi ) / 12 . If one side of the triangle has a length of 8 , what is the longest possible perimeter of the triangle?

1 Answer
Oct 22, 2016

The perimeter is 61

Explanation:

Let /_A = pi/12
Let /_B = (5pi)/8
Then /_C = pi - (5pi)/8 - pi/12 = (24pi)/24 - (15pi)/24 - (2pi)/24 = (7pi)/24

Let side a be the side opposite /_A with length 8. We do this because associating the given side with the smallest angle will yeild the largest perimeter.

Using the Law of Sines we can write the equation for sides b and c:

b = asin(/_B)/sin(/_A)
c = asin(/_C)/sin(/_A)

Let p = the perimeter

p = a + a(sin(/_B) + sin(/_C))/sin(/_A)

p = 61