In the figure, a circle touches all the four sides of a quadrilateral $ A B C D $ with $ A B=6 \mathrm{~cm}, B C=7 \mathrm{~cm} $ and $ C D=4 \mathrm{~cm} . $ Find $ A D $. "
Given:
A circle touches all the four sides of a quadrilateral \( A B C D \) with \( A B=6 \mathrm{~cm}, B C=7 \mathrm{~cm} \) and \( C D=4 \mathrm{~cm} . \)
To do:
We have to find \( A D \).
Solution:
Let $AD = x$
$AP$ and $AS$ are the tangents to the circle.
This implies,
$AP = AS$
Similarly,
$BP = BQ$
$CQ = CR$
$DR = DS$
Therefore,
$AP+BP+DR+CR=AS+BQ+DS+CQ$
$AB + CD = AD + BC$
$6 + 4 = 7 + x$
$10 = 7 + x$
$x = 10 - 7$
$x= 3$
Therefore, $AD=3\ cm$.
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