McGraw Hill Integrated II, 2012
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McGraw Hill Integrated II, 2012 View details
4. Parallel Lines and Proportional Parts
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Exercise 64 Page 581

Since S is the incenter of triangle PLJ, SQ and KS are congruent.

8

Practice makes perfect
Let's begin with recalling the Incenter Theorem. The angle bisectors of a triangle intersect at a point called the incenter that is equidistant from the sides of the triangle. Since we are given that S is the incenter of triangle PLJ, SQ and KS are congruent.
As â–ł JQS is a right triangle, we can use the Pythagorean Theorem to evaluate the length of QJ. According to this theorem, the sum of the squared legs of a right triangle is equal to its squared hypotenuse. QJ^2+SQ^2=JS^2 In the previous exercise we found that SQ has a length of 6, and we are given that the length of JS is 10. Using this information, we can find the length of QJ.
QJ^2+SQ^2=JS^2
QJ^2+ 6^2= 10^2
QJ^2+36=100
QJ^2=64
â–Ľ
sqrt(LHS)=sqrt(RHS)
sqrt(QJ^2)=sqrt(64)
QJ=sqrt(64)
QJ=8
The length of QJ is 8.