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an isosceles triangle has perimeter 30 CM and each of the equal sides is 12cm.find the area of triangle

Posted by Santosh Jha 8 years, 6 months ago

CBSE > Class 09 > Mathematics

1 answers

Rashmi Bajpayee 8 years, 6 months ago

Perimeter of Isosceles triangle = 30 cm

Each of equal side of given triangle = 12 cm

Let the third side be x cm

=> 12 + 12 + x = 30

=> x = 30 - 24 = 6 cm

Now, Semi-perimeter (s) = {tex}{{30} \over 2} = 15{/tex} cm

Using Heron's formula,

Area of given triangle = {tex}\sqrt {s\left( {s - a} \right)\left( {s - b} \right)\left( {s - c} \right)} {/tex}

= {tex}\sqrt {15\left( {15 - 12} \right)\left( {15 - 12} \right)\left( {15 - 6} \right)} {/tex}

= {tex}\sqrt {15 \times 3 \times 3 \times 9} {/tex}

= {tex}9\sqrt {15} {/tex} sq. cm

= 9 x 3.87

= 34.83 sq. cm

0Thank You

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