Area of a circle as follows. Draw a perpendicular from the center to the midpoint of a side of the polygon; its length, "h", is less than the circle radius. Also, let each side of the polygon have length "s"; then the sum of the sides, "ns", is less than the circle circumference. The polygon area consists of "n" equal triangles with height "h" and base "s", thus equals ⁄"nhs". But since "h" < "r" and "ns" < "c", the polygon area must be less than the triangle area, ⁄"cr", a contradiction. Therefore, our supposition that "C" might be greater than "T" must be
Mohr's circle points formula_117 on the Mohr circle and the centre of the circle. This double angle relation comes from the fact that the parametric equations for the Mohr circle are a function of formula_35. It can also be seen that the planes formula_80 and formula_81 in the material element around formula_7 of Figure 5 are separated by an angle formula_135, which in the Mohr circle is represented by a formula_136 angle (double the angle). The second approach involves the determination of a point on the Mohr circle called the "pole" or the "origin of planes". Any straight line drawn from the