A triangle has two corners with angles of ( pi ) / 4 π4 and ( 7 pi )/ 12 7π12. If one side of the triangle has a length of 7 7, what is the largest possible area of the triangle?

1 Answer
Oct 25, 2016

Largest possible area of the triangle is 33.46733.467

Explanation:

As two angles of a triangle are pi/4π4 and (7pi)/127π12, the third angle is

pi-pi/4-(7pi)/12=(12pi-3pi-7pi)/12=(2pi)/12=pi/6ππ47π12=12π3π7π12=2π12=π6

All triangles with these angles are similar. As length of one side is 77, its area will be maximum, if this side is opposite smallest angle i.e. pi/6π6.

Area of a triangle given one side a=7a=7 and two angles /_A=pi/6A=π6, /_B=pi/4B=π4 and /_C=(7pi)/12C=7π12 is

(a^2sinBsinC)/(2sinA)a2sinBsinC2sinA

= (7^2sin((7pi)/12)sin(pi/4))/(2sin(pi/6))72sin(7π12)sin(π4)2sin(π6)

= (49xx0.9659xx0.7071)/(2xx0.5)49×0.9659×0.70712×0.5

= (49xx0.0.683)/149×0.0.6831

= 33.46733.467