A triangle has vertices A, B, and C. Vertex A has an angle of pi/2 π2, vertex B has an angle of ( pi)/4 π4, and the triangle's area is 21 21. What is the area of the triangle's incircle?

1 Answer
Jun 7, 2016

The area of triangle's incircle is 11.3(1dp)11.3(1dp) sq.unit

Explanation:

The three angles are /_A= 180/2=90^0 ; /_B=180/4=45^0 ; /_C=180-(90+45)=45^0A=1802=900;B=1804=450;C=180(90+45)=450 This is a right angled isocelles triangle. The sides opposite to the angles/_B and /_CBandC are equal and their included angle is 90^0900. So the area of the triangle 21= 1/2*b^2 :. b =sqrt 42=6.48=c :.a=sqrt(6.48^2+6.48^2)=sqrt 84=9.17 So semi perimeter of the triangle s= ((6.48+6.48+9.17)/2) =11.06 Hence the radius of the incircle is r=A_t/s=21/11.06=1.9 ; A_t is area of triangle. Hence the area of triangles incircle is pi*r^2 = pi* 1.9^2 =11.3(1dp)sq.unit [Ans]