Intersection Problem - Beginner

I have a small beginner problem - plese see the picture attached.

I would like to move the open triangle straight down until the two “arms” intersects with the circle. I cannot come up with a solution.
I tried to google the topic but could not find a proper description to search for.

Thank you for your help!

As a beginner, I would use the Circle-tangent-tangent-radius tool and make a circle on the arms at the same radius as the existing circle, then just move those down where the original circle is and delete one of the circles. There may be a more ellegant way to do the perp-perp move on the arm, but I dont know what that is yet…

brilliant! worked well. thank you!