What is the area of an isosceles triangle with two equal sides of 10 cm and a base of 12 cm?

1 Answer
Nov 21, 2015

Area =48=48 cm^2cm2

Explanation:

Since an isosceles triangle has two equal sides, if the triangle is split in half vertically, the length of the base on each side is:

1212 cmcm-:2 = ÷2=66 cmcm

We can then use the Pythagorean theorem to find the height of the triangle.

The formula for the Pythagorean theorem is:

a^2+b^2=c^2a2+b2=c2

To solve for the height, substitute your known values into the equation and solve for aa:

where:
aa = height
bb = base
cc = hypotenuse

a^2+b^2=c^2a2+b2=c2
a^2=c^2-b^2a2=c2b2
a^2=(10)^2-(6)^2a2=(10)2(6)2
a^2=(100)-(36)a2=(100)(36)
a^2=64a2=64
a=sqrt(64)a=64
a=8a=8

Now that we have our known values, substitute the following into the formula for area of a triangle:

base = 12base=12 cmcm
height = 8height=8 cmcm

Area=(base*height)/2Area=baseheight2

Area=((12)*(8))/2Area=(12)(8)2

Area=(96)/(2)Area=962

Area=48Area=48

:., the area is 48 cm^2.