Acircle has its center at (0,0) and passes through the point (0,9). what is the standard equation of the circle?

answer:

When naming the similar triangles you want to go by which angles are equal to each other which they show with a line, or a couple of lines, which ever angles have the same lines than they are equal to each other

<A=<D, they both have one curved line

<B=<E, both don't have a line on them

<C=<F, both have two curved lines

Now when putting them in order you want to be sure to have the angles match up in the same order

ABC=DEF

They are in order from their similar angles, A and D are both first, then B and E, last C and F

Hope this helps explains things ;)