Question

A,B C are the vertices of a triangle,

B C = 3.9cm and

<ABC = 124 degrees,

the area is 6.4cm

what is the perimeter?

Answer 1

Area of triangle=½(3.9)ABsin124=1.95AB(0.829)=1.6166AB=6.4, so AB=6.4/1.6166=3.9589 approx.

Use the cosine rule to find the third side=√(AB²+BC²-2AB.BCcos124)=

√(15.6726+15.21-2(3.9589)(3.9)(-0.5592))=6.939 cm approx.

Perimeter=3.9589+3.9+6.939=14.7979cm approx.