Infinitely many. There are infinitely many lines from the apex to the base. Every point on each of these lines is on the surface of the cone.
Each of the four lines is perpendicular - to two of the other lines.
18 lines-6 of each color.
Pi has 2 lines of symmetry
The three lines making up a triangle do not intersect (cross) each other. Two lines join at each corner of the triangle.
It has two lines of symmetry, one each perpendicular to each other passing thru the center of the rectangle
Perpendicular lines = lines which are at right angles (90 degrees) to each otherDiamond = 2 pairs of parallel lines
None but its diagonals are perpendicular lines intersecting each other at right angles.
7, one for each corner.
Infinte
approx. 3 of each....
All squares have two pairs of parallel lines. That's four lines, but they are not all parallel to each other.