Let P cosh ob sinh b be the point on the hyperbola orrespond
     Let P (cosh ob, sinh b) be the point on the hyperbola orresponding to r(b) for ob> 0. Use the formula for area dy y dx to verify that the area of the region shown in the figure is job.  
  
  Solution
x = cosh, y = sinh
 dx = sinh, dy = cosh
 xdy = cosh^2d
 ydx = sinh^2d
 putting values in A
 A = 1/2 integral of [cosh^2 - sinh^2]d
 A = 1/2 integral of d [because cosh^2 - sinh^2 = 1]
 A = 1/2 ......hence proved

