Question 1024009
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the centers of two circles of radii 3 and 5 are 17 units apart. find the length of a common external tangent.
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The two radii must be perpendicular to the common external tangent, hence the length should be {{{sqrt(17^2 - (5-3)^2) = sqrt(17^2 - 2^2) = sqrt(285)}}}.


See the lesson <A HREF=https://www.algebra.com/algebra/homework/word/geometry/HOW-TO-construct-a-common-exterior-tangent-line-to-two-circles.lesson>HOW TO construct a common exterior tangent line to two circles</A> (Problem 2) in this site.