Question

7. The area of an isosceles triangle having
base 2 cm and the length of one of the
equal sides 4 cm, is
(a) V15 cm?
(b)
V 2
(c)2/15 cm?
(d)4/15 cm?
15
cm?​

Answer 1

★ Given :

• Base of an isosceles triangle is 2 cm.

• The length of one of the equal sides is 4 cm.

★ To find :

• The area of an isosceles triangle =??

★ Solution :

Let ,

• a = 4cm
• b = 4 cm
• c = 2 cm

Using Heron's formula as:

${\underline { \boxed { \bf { \red{A=\sqrt{s(s-a)(s-b)(s-c)}}}}}} \: \green \bigstar$

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

$: \implies \tt \: s=\dfrac{4+4+2}{2}$

$: \implies \tt \: s=5 \: cm$

Now using the above formula as :

$:\implies\tt \: A=\sqrt{5\times (5-4)(5-4)(5-2)}$

$: \implies \tt \: A=\sqrt{5\times 1\times 1\times3}$

$: \implies\tt \: A=\sqrt{15} \ cm^2$

So, the area of an isosceles triangle is

$\bf\sqrt{15}$