$\angle FBF = 90°, FB \perp FB$

એટલે $(FB)$ નો ઢાળ $(FB)$ નો ઢાળ $= -1$

$ \Rightarrow \,\,\frac{b}{{ae}}\,\, \times \,\,\frac{b}{{ – ae}}\,\, = \,\, – 1,\,\,{b^2}\,\, = \,\,{a^2}\,{e^2}\,\,\,….\,\,\left( i \right)$

આપણે જાણીએ છીએ કે $\,e\,\, = \,\,\sqrt {1\,\, – \,\,\frac{{{b^2}}}{{{a^2}}}} \,\, = \,\,\sqrt {1\,\, – \,\,\frac{{{a^2}{e^2}}}{{{a^2}}}} \,\, = \,\,\sqrt {1\,\, – \,\,{e^2}} $

${e^2}\,\, = \,\,1\,\, – \,\,{e^2},\,\,2{e^2}\,\, = \,\,1,\,\,{e^2}\, = \,\,\frac{1}{2},\,\,e\,\, = \,\,\frac{1}{{\sqrt 2 }}$