How to draw a ray diagram for a concave mirror with conditions?

Question

Can someone please tell me how to draw a ray diagram (with 3 rays) for a concave mirror that has no focal point given?

It it place like this: (sorry I don't have images)

Object... Point of Curvature of radius.... concave mirror.

It's something like this: http://www.glenbrook.k12.il.us/gbssci/phys/mmedia/optics/rdcmd.gif except that the object is at far end and comes before the C and there's no F given!

I know how to draw the rays for a diagram like this in general, but there's no focal point given, and I don't know how should a draw 3 rays without the focal point! I've got one of the rays, the one that goes straight through the C, but I need two more and Id on't have a clue how!

I really this urgent, it's due very soon, so someone please help me!

Answer 1

The focal length is one-half of the radius of curvature. So, it will be half-way between C and the mirror.

Sounds like you know how to take it from there. Good luck!