Area of an isosceles triangle whose base is 18 cm and one of it's equal is 15 cm
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Step-by-step explanation:
In the above isosceles triangle
AB= 15cm
AC= 15cm
BC= 18cm
BD=18÷2=9cm
AD is the altitude.
according to Pythagorean Theorem
(AD)^2 + (BD)^2 = (AB)^2
(AD)^2 + (9) ^2 = (15) ^2
(AD)^2 + 81 = 225
(AD)^2 = 225 - 81
(AD)^2 = 144
Therefore, AD = √144 = 12cm
Now,
Area of the triangle
= 1/2 × base × height
=1/2 × BC × AD
=(1/2 × 18 × 12)
= 108 sq cm
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