On a sphere you can draw a triangle with three right angles. . At the North pole , zero meridian and its right angle 90 oW merdian. Draw these meridians to the Equator, and you will find they both meet the Equator at 90 o (degrees).
triangle
Number all the structural degrees of freedom in your truss. In a 2D (planar) truss, each joint can have a maximum of two degrees of freedom: one in the global X-direction and one in the global Y -direction. If a degree of freedom is restrained by a reaction, then it doesn't get a number.
a simple 2d xy line graph has only the possibility for 2 different variables (x and y). for a 3 variable graph you would have to go into a 3d xyz graph with each variable as x, y and z. it is possible to fit a line to this but for an easier analysis it is better to analyse the variables in pairs.
No
rhombus
Squares
A rhombus is one of them
This is the desctiption of a rectangle. It mightbe a square, but it does not have to be one.
A rhombus. (Which is in fact also an equilateral parallelogram)
Squares
A square is a two-dimensional shape with four equal sides and four right angles.
Polygon
A cyclic kite. A kite is cyclic if it has only two right angles.
4
A square