Question

circle o is inscribed in triangle rst such that it is tangent at points m,n, and p. if rp is 7, rt is 17 and sm is 5, then what is the length of side st?

Answer 1

The length of side st is 15.

Explanation:

A tangent is a straigth line that touches a circle externally at a point on the circumference. Considering one of its properties that tangents from the same point to a fixed point outside a circle are equal.

Then,

/rn/ = /rp/

/tm/ = /tn/

/sm/ = /sp/

But, /rp/ = 7, /rt/ = 17 and /sm/ = 5.

Then,

/rt/ = /rn/ + /tn/

17 = 7 + /tn/ (∵ /rp/ = /rn/ = 7)

⇒ /tn/ = 10

Since /nt/ = 10, then /tm/ = 10 (/tm/ = /nt/)

So that,

/st/ = /sm/ + /tm/

= 5 +10

/st/ = 15

The length of side st is 15.