1. A circle centered at A with radius 10 is externally tangent to a circle centered at B with radius 7. A line that is externally tangent to both circles intersects line AB at C. Find the length BC.
3. 
1. By similar triangles, BC = 13*10/7 = 130/7.
3. By similar triangles, YZ = 14^2/8 = 49/2.
+1490 1) A circle centered at A with radius 10 is externally tangent to a circle centered at B with radius 7. A line that is externally tangent to both circles intersects line AB at C. Find the length BC.
BC = 39.66666672 
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2) AB = 2 x = 1 CD = 4.5 y = 2.25
r = sqrt ( xy ) = sqrt ( 1 * 2.25 ) = 1.5
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3) XY = 14 WX = 8
tan(Y) = 8 / 14 ∠Y = 29.7448813°
XZ = tan(Y) * WX = 4.571428571
YZ = XY - XZ = 9.428571429
YZ ≈ 9.428
+118667 Question 3
The guest here https://web2.0calc.com/questions/help-asap_85440
Says that Dragan's answer is incorrect.
So I graphed it to scale.
I got the same answer as Dragan. (they are both approximate)
*Although Dragan has not used universal logic.
He has looked at the specific case where WY is a diameter of the circle.
And then he has assumed that it will be the same in all other cases as well.
https://www.geogebra.org/classic/avx3arkb
