Question 1143360
The tangent to the circle makes a 90 degree angle with the radius
One leg of the right triangle is 9 mm
The hypotenuse is 12 mm
{{{ a^2 + b^2 = c^2 }}}
{{{ a^2 + 9^2 = 12^2 }}}
{{{ a^2 = 144 - 81 }}}
{{{ a^2 = 63 }}}
{{{ a = 7.937 }}}
The radius is 7.937 mm