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In the figure, AB is a tangent to the circle at B. DECA is a straight line and OEtangentDC. If AB=20, AC=10 and the radius of the circle is 18,

a) find the length of OA
b) By considering triangleODE, express y in terms of x
c) By considering triangleOAE, express y in terms of x
d) Hence find x and y

a) find the length of OA

consider triangle ABO, angle ABO = 90 degrees
by pyth theorem, get AO = suqare root 724

b) By considering triangleODE, express y in terms of x
y square = 324 - x square

c) By considering triangleOAE, express y in terms of x

(10+x) square + y square = 724

d) Hence find x and y
From (b) and (c), two equations two unknowns, DO IT YOURSELF!