# An equilateral triangle has side lengths of 10 the length of its altitude a is ?

I need help I’m not sure if I’m right or not Relevance
• Yes you are right it is option (D) by using Pythagoras' theorem.

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• h^2=s^2-b^2

=(s+b) *(s-b)

h^2= 15*5=75

h=sqrt 75=8.66

h=height,b=base,s=slant

you are right

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• Height of the equilateral triangle is found by taking the length of one side time the square root of 3 and then divide by 2. If you can't do that, then you really need to see your teacher because this is only going to get harder for you.

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• Mentally draw a straight line from the high point of the triangle, straight down to the base. This is the altitude.

This line — we will call side “a” — is also one side of a right triangle. The base of the right triangle, which we will call side “b”, is 1/2 of one side of the equilateral triangle, or 5 units. The hypotenuse — the longest side of the right triangle that we will call side “c” — is the side of the equilateral triangle, or 10 units.

Using the Pythagorean Theorem:

a2 + b2 = c2, where “c” is the hypotenuse.

So... plug in your values for “b” (5) and “c” (10) and solve for “a”. This is the altitude.

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