Question 288509
Find  the  area  of  an  equilateral 
triangle  with  a  side  length  of  15 cm.
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Draw the equilateral triangle.
Draw an altitude from the top vertex 
perpendicular to the base.
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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
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Area = (1/2)base*height
A = (1/2)15*12.99
A = 97.42 sq. cm.
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Cheers,
Stan H.