A triangle has vertices A, B, and C. Vertex A has an angle of pi/3 π3, vertex B has an angle of (5 pi)/12 5π12, and the triangle's area is 16 16. What is the area of the triangle's incircle?

1 Answer
Jan 9, 2018

Area of I’m circle color(green)(A_i = 9.19) sq. UnitsAi=9.19sq.Units

Explanation:

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Given A = pi /3, B = (5pi) / 12, C = pi - A - B = pi / 4A=π3,B=5π12,C=πAB=π4

Area of triangle A_t = 16At=16

a*b = A_t / ((1/2) sin C) = 16 / (0.5 sin (pi/3)) ~~ 36.95ab=At(12)sinC=160.5sin(π3)36.95

Similarly,
b*c = 16 / (0.5 sin A) = 16 / (0.5 * sin ((5pi)/12)) ~~ 33.13bc=160.5sinA=160.5sin(5π12)33.13

c*a = 16 / (0.5 sin B) = 16 / (0.5 * sin (pi/4)) ~~ 45.25ca=160.5sinB=160.5sin(π4)45.25

(ab * bc * ca) = (abc)^2 = 36.95 * 33.13 * 45.25 = 55392.95(abbcca)=(abc)2=36.9533.1345.25=55392.95

abc = sqrt(55392.95) ~~ 235 36abc=55392.9523536

a = (abc) / (bc) = 235.36 / 33.13 ~~ 7.1a=abcbc=235.3633.137.1

b = (abc) / (ca) = 235.36 / 45.25 ~~ 5.2b=abcca=235.3645.255.2

c = (abc) / (ab) = 235.36 / 36.95 ~~ 6.37c=abcab=235.3636.956.37

Semi perimeter S/ 2 = (a + b + c) / 2 = (7.1 + 5.2 + 6.37) / 2 = 9.34S2=a+b+c2=7.1+5.2+6.372=9.34

In radius r = A_t / (S/2) = 16 / 9.34 = 1.71r=AtS2=169.34=1.71

Area of in circle A_i = pi r^2 = pi * (1.71)^2 = color(green)(9.19)Ai=πr2=π(1.71)2=9.19