drawing a radius tangent to two circles

Hi guys just getting into Librecad and would like to know the easiest way to draw the radius of 105 with an arrow pointing to it in the pic
thanks

If you really mean a radius tangent to two circles, it's Circle - Tangential Two Circles, Radius. Cut open the r 105 circle at the tangent points (snap intersection on) and delete the unwanted part.
But in the picture it looks like the 105 radius instead intersects with the upper left circle at it's left quadrant. Something different, I don't know a solution for that.

Hi Dellus, thanks for the reply, I've tried tangential 2 circles radius and cant seem to get it to work, it allows me to pick the first circle. but when I click on the other circle it doesn't recognize it.

Probably the radius, which is set in the tool options bar above the drawing area, is too small to make a tangent.

Brilliant Dellus thanks, it worked, now as to the problem with quadrant intersection, I will be sending 2d drawings for the production of templates for tooling, any idea of the margin of error if it doesn't intersect precisely with the quadrant, thanks again

With the given circles the tangent will never meet the quadrant. You have to decide what is more important for your design, to have a true tangent or to meet a certain point. The tangent meeting point on the lower circle might also be defined by an angular position on the circle instead. In this case you could use Circle - 2 Points, Radius.
It's bedtime for me now.
And I have just ruined my keyboard by spilling beer over it. Behaves erratically.
Writing this now with an ancient notebook kept as backup.

Good night.

thanks Dellus, sorry to hear about your keyboard, it has happened us all, beer is still good though