Two corners of a triangle have angles of (5 pi ) / 12 5π12 and (3 pi ) / 8 3π8. If one side of the triangle has a length of 2 2, what is the longest possible perimeter of the triangle?

1 Answer
Jun 26, 2017

The perimeter is =8.32=8.32

Explanation:

The third angle of the triangle is

=pi-(5/12pi+3/8pi)=π(512π+38π)

=pi-(10/24pi+9/24pi)=π(1024π+924π)

=pi-19/24pi=5/24pi=π1924π=524π

The angles of the triangle in ascending order is

5/12pi>9/24pi>5/24pi512π>924π>524π

To get longest perimeter, we place the side of length 22 in front of the smallest angle, i.e. 5/24pi524π

We apply the sine rule

A/sin(5/12pi)=B/sin(3/8pi)=2/sin(5/24pi)=3.29Asin(512π)=Bsin(38π)=2sin(524π)=3.29

A=3.29*sin(5/12pi)=3.17A=3.29sin(512π)=3.17

B=3.29*sin(3/8pi)=3.03B=3.29sin(38π)=3.03

The perimeter is

P=2+3.29+3.03=8.32P=2+3.29+3.03=8.32