Question

Find the area of the equilateral triangle with sides 10 cm..

Ans is supposed to 43.3cm^2 (according to the answer sheet) but no workings are given :(

Answer 1

ar of equilateral triangle=root3/4a^2

Answer 2

First, divide in one of his heights the triangle into two triangles with a right angle (90, 60, 30 will be their angles).
Then, you have 10 cm of hypothenuse, and 5 of base.
You want to know the height.
10^2=height^2-5^2
75=height^2
sqrt(75)=height
Then height*5/2 *2 (because you have 2 triangles)
height*5=sqrt(75)*5=25*(sqrt(3))=43.3012~ cm2

Answer 3

x^2+25=100
x=5(3)^1/2
Area=1/2*10*5(3)^1/2
=25(3)^1/2/2
=43.301cm^2