Is it possible for an equalateral triangle to consist of three 90 angles?
When you draw an equilateral triangle on the surface of a sphere, each angle is greater than 60 degrees. As the sphere gets smaller, the angle-size gets larger. Can it reach 90 degrees, or is that approached as a limit?
I don't know.
Yes, it can reach 90 degress at all three angles on a sphere.
Consider drawing two line segments southward from the North Pole, with a 90 degree angle between them, until they reached the Equator. The angles of the intersections of those lines at the Equator would also be 90 degrees, giving you three at 90.
Can the angles be greater than 90 degrees? Not so certain about that one! In order for that to happen in three dimensions, I belive it couldn't be eualateral. I believe that 90 degrees is the maximum in three dimensions for an equalateral triangle.