MN2 = NH.PN
MP2 = PH.PN
MH2 = NH.PH
\(\dfrac{1}{MH^2}=\dfrac{1}{MN^2}+\dfrac{1}{PM^2}\)
MN.MP = MH.PN
\(MN^2=NH\cdot NP\); \(MP^2=PH\cdot PN\)
\(MH^2=HN\cdot HP\)
\(\dfrac{1}{MH^2}=\dfrac{1}{MN^2}+\dfrac{1}{MP^2}\)
\(MH\cdot NP=MN\cdot MP\)
\(NP^2=MN^2+MP^2\)