Question

An isosceles triangle has perimeter 30 cm and each of its equal sides is 12 cm. Find its area. use root15 as. 3.88

Answer 1

base of triangle =30-12-12=6
altitude divide the base
so
by Pythagoras theorem
altitude^2 =12^2 - 3²
altitude =11.6
area =1/2base*height =1/2*11.6*6=34.8cm2

Answer 2

Step-by-step explanation:

Perimeter of isosceles triangle=30cm

Length of equal sides=12cm

Let third side of triangle=xcm

According to problem,

x+12+12=30

x+24=30

x=30−24

x=6

∴ Third side of triangle=6cm

Using Heron's formula

Area of triangle=s(s−a)(s−b)(s−c) sq. units

where s=2a+b+c

s=230=15

Area of triangle=15(15−12)(15−12)(15−6)cm2

= 15×3×3×9cm2

=3×3×15cm2

=915cm2

∴ Area of triangle=915 cm 2 .