Contour line factors in a weather system. An isobar (from or "baros", meaning 'weight') is a line of equal or constant pressure on a graph, plot, or map; an isopleth or contour line of pressure. More accurately, isobars are lines drawn on a map joining places of equal average atmospheric pressure reduced to sea level for a specified period of time. In meteorology, the barometric pressures shown are reduced to sea level, not the surface pressures at the map locations. The distribution of isobars is closely related to the magnitude and direction of the wind field, and can be used to predict
Group of rational points on the unit circle to the origin, equal to 0. The identity in this larger group is (1,0,1,0), and the group operation is formula_9 For the group on the unit circle, the appropriate subgroup is points of form ("w","x",1,0), with formula_10 and its identity element is (1,0,1,0). The unit hyperbola group corresponds to points of form (1,0,"y","z"), with formula_11 and the identity is again (1,0,1,0). (Of course, since they are subgroups of the larger group, they both must have the same identity element.) Group of rational points on the unit circle In mathematics, the rational points on the unit circle are those points ("x",