Bunuel
One of the sides of a triangle that inscribe in a circle is 6. Is the triangle a right triangle?
(1) Two of the sides of the triangle have the same length. Know nothing about the circle. Not sufficient.
(2) The circumference of the circle is 6 pi --> \(2\pi{r}=6\pi\) --> \(r=3\) --> \(diameter=6\). So, one of the sides of the triangle is the diameter of the circle. Now, a right triangle inscribed in a circle must have its hypotenuse as the diameter of the circle. The reverse is also true: if the diameter of the circle is also the triangle’s side, then that triangle is a right triangle. Sufficient.
Answer: B.
Hello Bunuel,
Why can't we conclude from the first statement that the triangle is not a right angle since it is said to be an isosceles triangle? Since the triangle is inscribed in a circle, I think the only way for a triangle to be isosceles is when the two sides of the triangle are the radii of the circle. Please inform me where my understanding might be wrong.