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Find the area of an equilateral triangle whose base is 10 cm.

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2 answers
  1. 2 right angled triangles = 1 equilateral triangle. You can pretty much split it down the middle and you'll see the 2 triangles from.

    The formula for a right angle triangle is:
    (b x h)/2 = area

    If we were solving for 1/2 the triangle we know that the base is 5 cm, the height is unknown and the hypotenuse is 10 cm.

    Using Pythagorean theorem we can solve for the height:
    a^2 + b^2 = c^2
    5^2 + b^2 = 10^2
    25 + b^2 = 100
    b^2 = 75
    b = about 8.66

    Now we can plug this value for our height back into the equation:
    (b x h)/2 = area
    (5 x 8.66)/2 = area
    21.65 cm^2

    Remember this is only 1/2 of the triangle so you could multiple by 2 (or simply do not divide my 2 in the above equation):
    Area of equilateral triangle = 43.30 cm^2

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  2. This is an awesome app.

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