Thread: Circles

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?

What is the dot on the line in #4. Is that line supposed to be a diameter?

-Dan

Yes... ............

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