<PRE><B>Question 668359</B>
Since AD is the altitude to base BC we have to find AD &amp; DC

Two right triangles are formed .
ABD &amp; ACD

In triangle ABD
BD= 10
AB= 15

Apply Pythagoras theorem
AB is the hypotenuse
{{{15^2-10^2= AD^2}}}

225-100=AD^2
125 = AD^2
{{{AD = 5 sqrt(5)}}}

We have AC= 18
AD= {{{5sqrt(5)}}}

{{{DC^2= 18^2-(5sqrt(5))^2}}}

{{{DC^2=324-125}}}

{{{DC^2=199}}}

{{{DC = sqrt(199)}}}

BD+DC= BC

{{{BC = 10 +sqrt(199)}}}

Area of triangle = 1/2 base * altitude
={{{1/2 * (10+sqrt(199))*5sqrt(5)}}}

By using calculator you will get 134.76 sq. cm

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