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radius of incircle triangle?

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by kvcpk » Thu Jun 17, 2010 2:34 am
francoisph wrote:What is the radius of the incircle of the triangle whose sides measure 5, 12 and 13 units?
triangle with sides 5,12 ,13 is a right angled triangle.

Raius of incircle = 2(area of triangle)/(sum of sides)
= 2(1/2 * 5 * 12) / (5+12+13)

=60/30 = 2 units
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by amising6 » Thu Jun 17, 2010 2:35 am
now let us first find area of triangle usinh hero formula i.e a=p
Area= squareroot of(s (s − a) (s − b) (s − c))
where s=(a+b+c)/2
s=5+12+13/2=15
now area will be squareroot of(15 (15 − 5) (15 − 12) (15 − 13))
area=30
so radius r=
r = 2A/a + b + c
r=2*30/(5+12+13)=2
ans 2
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