Math
posted by Jane .
An equilateral triangle is one in with all three sides are length. If two vertices of an equilateral trangle (0,4) and (0,0), find the third vertex. How mant of these triangles are possible?
How would you slove this??

Thre are two possible solutions, with the third vertex to the right or left of the y axis. The side length is obviously 4 and the base is along the y axis.
The y value of the third vertex is +2 .
For the x value,
x^2 + 2^2 = 4^2 (The square of the length of a side)
x = + or  sqrt 12 
Okay I get everything but the
For the x value,
x^2 + 2^2 = 4^2 (The square of the length of a side)
x = + or  sqrt 12
How did you get that and why??