A triangle has vertices A, B, and C. Vertex A has an angle of pi/2 π2, vertex B has an angle of ( pi)/6 π6, and the triangle's area is 72 72. What is the area of the triangle's incircle?

1 Answer
Feb 12, 2017

Area of triangle's incircle is 35.04(2dp)35.04(2dp) sq.unit.

Explanation:

/_A= pi/2=90^0 ; /_B= pi/6=30^0 ; /_C =180-(90+30)=60^0A=π2=900;B=π6=300;C=180(90+30)=600

This is a 30-60-90306090 triangle. So ifAC=xAC=x then AB=x*sqrt3; ;BC=2xAB=x3;;BC=2x, Area of triangle is 1/2*AB*AC =72 or x*sqrt3*x=72*2 or x^2=144/sqrt3 :.x = 9.12(2dp) ; 2x=18.24(2dp) ; sqrt3x=15.79
Sides of triangle are 9.12,15.79 &18.24unit
Perimeter of triangle is P= 9.12+15.79 +18.24 =43.15 unit
Area of triangle is A_t=72sq.unit
Radius of triangle's incircle is r=(2*A_t)/P=(2*72)/43.15= 3.34(2dp)unit
Area of triangle's incircle is A_r= pi* *r^2=pi*3.34^2 = 35.04(2dp)sq.unit. [Ans]