Projections Check: Find Real Size of Sphere Beam

[DarkART]

Homework Statement

Are given points A (a ', a) and point B (b', b) and horizontal projection of point Q (q)
REQUIRED
real size of the beam of sphere with center Q and A and B are points on its surface.

Homework Equations

The Attempt at a Solution

This is a problem i solved at a test at school!
But I am 90% that is corect ?I need a check for this ?Pls

 

[DarkART]

Some expalanation...

1.after I find the point q 'I do so to find the radius of the sphere
J 2.build the plan J (orange) that's si parallel with Ox in Horizontal ... plan J cross from b and expects the line ab at point 1
3.finde its projection on V. .. point 1 '.
4.build a new shaft X1 O1 (red line) perpendicular to the plain J
5.build design points a'b 'a' q '...
6.result is an interconnect (a line with all the points)(green line)
crate a new axle O2 x2 ...thats parallel with the greend line
8.build the projections of points ... and the triangle formed is in its rala size ... 2 equal rib demonstrating that the points A and B on the surface
9.from the Q build the circle flowing from b and a. ..
10. QA QB are the radius of the circle ... the sphereso what do u think ?? is this correct?