The length of the direct common tangent to two circles of radii 12cm and 4cm is 15cm.Calculate the distance between their centres. 

Asked by prodyumna02 | 11th Feb, 2019, 03:23: PM

Expert Answer:

Construct EC||AB
AB=15cm=EC
AD=12 cm
CB=4 cm
DE=12-4=8
Tangent is perpendicular to radius
ABCE is rectangle
triangle DEC is a right-angled triangle
so 
DC2=DE2+EC2
DC=17

Answered by Arun | 11th Feb, 2019, 03:59: PM