# Circles

• May 12th 2007, 01:50 PM
melquan23
Circles
http://i2.tinypic.com/63248hv.jpg

I need help with my homework. My teacher's going to grade this and then this is our study sheet.
I had to scan the questions, since I couldn't draw it in paint.

Can someone please explain how to figure these out?
• May 12th 2007, 02:10 PM
topsquark
What is the dot on the line in #4. Is that line supposed to be a diameter?

-Dan
• May 12th 2007, 04:18 PM
melquan23
Yes... ............
• May 13th 2007, 06:36 AM
topsquark
Quote:

Originally Posted by melquan23
Yes... ............

Then you can finish this. :)

The formula you are looking for is that an angle whose vertex is on a circle that measures an arc has a measure of half the arc.

So the angle on the lower right measures an arc of 89 degrees, thus the angle is (1/2)*89 = 44.5 degrees.

The angle at the top of the triangle measures an arc of 180 degrees (since the chord it intesects is a diameter it measures half the circle) so the angle is (1/2)*180 = 90 degrees.

So your triangle has three angles: x, 44.5 degrees, and 90 degrees. The sum of the interior angles of a triangle has 180 degrees, so x = 180 - 44.5 - 90 = 45.5 degrees.

-Dan