ABC is a right angled triangled, right angled at C and P is the length of the perpendicular from C on AB. If a, b and c are the length of the sides BC, CA and AB respectively, then

• A. $\frac{1}{{{p^2}}} = \frac{1}{{{b^2}}} - \frac{1}{{{a^2}}}$$
• B. $\frac{1}{{{p^2}}} = \frac{1}{{{a^2}}} + \frac{1}{{{b^2}}}$$
• C. $\frac{1}{{{p^2}}} + \frac{1}{{{a^2}}} =- \frac{1}{{{b^2}}}$$
• D. $\frac{1}{{{p^2}}} = \frac{1}{{{a^2}}} - \frac{1}{{{b^2}}}$$