In $\triangle ABC$, the circumcenter and orthocenter are collinear with vertex $A$. Which of the following statements must be true?

(1) $\triangle ABC$ must be an isosceles triangle.

(2) $\triangle ABC$ must be an equilateral triangle.

(3) $\triangle ABC$ must be a right triangle.

(4) $\triangle ABC$ must be an isosceles right triangle.

Hints such as

"How should I draw this triangle?"

please

Guest Nov 10, 2019

#1**+5 **

Hint:

The circumcenter is where the perpendicular bisectors meet

The orthocenter is where the altitudes intersect

tomsun Nov 10, 2019

#4**0 **

If it is a genuine question you could at least present it properly.

Why have you left all those meaningless $ signs there.

To me this is an indication of laziness.

Melody Nov 10, 2019

#5**+2 **

You want hints?

ok

Find out what a circumcentre and a orthocentre is. Google is very helpful.

Now draw a triangle and roughly indicate where C and O. I suggest you draw an acute angled, isosceles triangle to start with.

Now think about the line from BC ot the circumcentre C.

How will the triangle have to change to get this to be the same line as BC to the orthocentre O

This will indicate at least on correct answer.

Now think about it (draw some more triangles) to see if any of the othes needs to be true as well

This took me some time to work out and then to check. It wil take you and brain power too.

**Please no one answer over me.**

Melody Nov 10, 2019