Question

4:- 3. The equal sides of the isosceles triangle are 12 cm, and the perimeter is 30 cm. The area of this triangle is:
9√15 (cm)
6√15 (cm)
3√15 (cm)
√15 (cm)

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Answer 1

Answer:

Hey mate!

Please see the attachment below.

The answer is $9\sqrt{15}cm^{2}$

Hope this helps :)

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Answer 2

Given :

• Two equal sides of an isosceles triangle are 12 cm each .
• Perimeter is 30 cm .

To Find :

• Area of Triangle .

Solution :

• a = 12 cm
• b = 12 cm
• c = ?

$\longmapsto\tt{a+b+c=30}$

$\longmapsto\tt{12+12+c=30}$

$\longmapsto\tt{24+c=30}$

$\longmapsto\tt{c=30-24}$

$\longmapsto\tt\bf{c=6\:cm}$

Now ,

$\longmapsto\tt{s=\dfrac{a+b+c}{2}}$

$\longmapsto\tt{s=\dfrac{12+12+6}{2}}$

$\longmapsto\tt{s=\cancel\dfrac{30}{2}}$

$\longmapsto\tt\bf{s=15\:cm}$

$\longmapsto\tt{Area=\sqrt{s(s-a)(s-b)(s-c)}}$

$\longmapsto\tt{\sqrt{15(15-12)(15-12)(15-6)}}$

$\longmapsto\tt{\sqrt{15\:(3)\:(3)\:(9)}}$

$\longmapsto\tt{\sqrt{5\times{3}\times{3}\times{3}\times{3}\times{3}}}$

$\longmapsto\tt{3\times{3}\sqrt{5\times{3}}}$

$\longmapsto\tt\bf{9\sqrt{15\:cm}{cm}^{2}}$

So , The Area of Triangle is 9√15 cm² ...