Two equal circles of radius 3 cm each and distance between their centres is 10 cm. The length of one of their transverse common tangent is

If radius of two circles are $$r_1$$ and $$r_2$$ cm and distance between their centres = $$d$$ cm

Then length of direct common tangent = $$\sqrt{(d)^2-(r_1-r_2)^2}$$

and length of transverse common tangent = $$\sqrt{(d)^2-(r_1+r_2)^2}$$

Here, $$r_1=r_2=r=3$$ cm and distance between centres = $$d=10$$ cm

=> Length of transverse common tangent = $$\sqrt{(10)^2-(3+3)^2}$$

= $$\sqrt{100-36}=\sqrt{64}=8$$ cm

=> Ans - (D)