An equilateral triangle has 3 lines of symmetry
An equilateral triangle has exactly three lines of symmetry. It is the only shape that contains exactly three lines of symmetry.
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Equilateral triangle
An equilateral triangle.
If your asking what shape has three lines of symmetry, your answer would be an equilateral triangle. You can tell how many lines of symmetry a shape that has all angles of the same measure has by looking at it's angles. Ex., pentagon has five angles--five lines of symmetry; octagon has eight angles, eight lines of symmetry; etc.
The shape that has three lines of symmetry is the equilateral triangle. It also has three angles of equal size and three sides of equal length.
It may have none, depending on its shape; the maximum is three.
It may have none, depending on its shape; the maximum is three.
Ah, what a happy little question! The shape you're thinking of is a scalene triangle. It doesn't have any lines of symmetry, but it does have rotational symmetry of order 4, which means it looks the same after being rotated 90 degrees four times. Isn't that just lovely?
A right angle triangle
Triangle * * * * * The only triangle with rotational symmetry of order 3 is an equilateral triangle and that has 3 lines of symmetry, not 0. The triskelion (the three legs) on the Isle of Man flag has rotational symmetry of order 3 but no lines of symmetry.