SOLUTION: I can't seem to figure out this problem. Please Help Me!! I have tried a million times and it just doesnt seem right. The actual problem is: {{{Find the area of an equilateral

Algebra ->  Triangles -> SOLUTION: I can't seem to figure out this problem. Please Help Me!! I have tried a million times and it just doesnt seem right. The actual problem is: {{{Find the area of an equilateral      Log On


   

Question 288509: I can't seem to figure out this problem. Please Help Me!! I have tried a million times and it just doesnt seem right. The actual problem is: Find++the++area++of++an++equilateral++triangle++with++a++side++length++of++15cm. First I tried plugging it into this formula: A=15squared(times the square root of 3 divided by 4) but I got this really weird number; something around 97. Can you help me??
Found 2 solutions by Alan3354, stanbon:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
Find the height.
h+=+sqrt%2815%5E2+-+7.5%5E2%29+=+15sqrt%283%29%2F2
Area = bh/2
Area+=+15%2A15sqrt%283%29%2F4
Area =~ 97.43 sq cm
What makes a number "weird?"

Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
Find the area of an equilateral
triangle with a side length of 15 cm.
-----------------------------------
Draw the equilateral triangle.
Draw an altitude from the top vertex
perpendicular to the base.
------------------------------
Use Pythagoras to find the length of the altitude.
15^2 = 7.5^2 + a^2
a^2 = 15^2-7.5^2
a^2 = 168.75
altitude = 12.99 cm
--------------------------
Area = (1/2)base*height
A = (1/2)15*12.99
A = 97.42 sq. cm.
=================================
Cheers,
Stan H.