The vertices of a triangle are A(1,1), B(0,0) and C(2,0). The angular bisectors of the triangle meet at P. What are the coordinates of P?

  1. A. (1,\sqrt{2}-1)
  2. B. (1,\sqrt{3}-1)
  3. C. (1,1/2)
  4. D. (1/2,\sqrt{2}-1)

Correct Answer: A. (1,\sqrt{2}-1)

Explanation

The intersection of angular bisectors is the incenter. The side lengths are a=BC=2, b=AC=\sqrt{1^2+(-1)^2}=\sqrt{2}, and c=AB=\sqrt{1^2+1^2}=\sqrt{2}. The incenter coordinates (x,y) are given by (\frac{ax_1+bx_2+cx_3}{a+b+c}, \frac{ay_1+by_2+cy_3}{a+b+c}). Thus x = \frac{2(1)+\sqrt{2}(0)+\sqrt{2}(2)}{2+2\sqrt{2}} = 1 and y = \frac{2(1)+\sqrt{2}(0)+\sqrt{2}(0)}{2+2\sqrt{2}} = \frac{1}{1+\sqrt{2}} = \sqrt{2}-1.

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