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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.

Hi,

I am not clear on the answer B. If a triangle is inscribed in the circle then it is definitely right angle. However, shouldnt we consider the option where two other sides are not in the circle and the triangle then formed could be an equilateral triangle or a scalene triangle - in which case the triangle is not a right angle. Please advise. thanks, Amita
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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.

Hi,

I am not clear on the answer B. If a triangle is inscribed in the circle then it is definitely right angle. However, shouldnt we consider the option where two other sides are not in the circle and the triangle then formed could be an equilateral triangle or a scalene triangle - in which case the triangle is not a right angle. Please advise. thanks, Amita

That's not correct. Any triangle can be inscribed in a circle: scalene, obtuse, right.

Also, inscribed triangle means that the vertices of the triangle are on the circle.
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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.
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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.

Check the image below:



Attachment:
Untitled.png
Untitled.png [ 20.15 KiB | Viewed 5674 times ]
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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.

Check the image below:



Attachment:
Untitled.png
Okay! Thanks!

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