share sketch between straight and tangence circle

[Giancesa]

I can't put a quota that starts from a straight and stands on the tangence of the circumference., on the photo you see the quota 5.38. I would like you to leave the tangent. In other words, when I go above the circle with the cursor, it only appears concentric or the top point. Thank you.

 

[LaboratorioDieci]

hold the shift key.

 

[MassiVonWeizen]

I didn't understand how you quoted.
when entering a quota there is no concentric bond or anything.
select the line and circle holding shift as it wrote @shirokkoHowever to me that quota seems correctly perpendicular to the line

 

[Giancesa]

Thanks, shift is perfect.