Geometryhard · Past Paper
Find the length of the direct common tangent to two circles of radii 12 cm and 7 cm, if the distance between their centers is 13 cm.
A5 cm
B12 cm
C10 cm
D11 cm
✓ Correct Answer: B — 12 cm
L = sqrt(d^2 - (r1-r2)^2) = sqrt(13^2 - (12-7)^2) = sqrt(169 - 25) = sqrt(144) = 12 cm.
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