Explanation:
First we consider ΔABC and ΔBCD,
∠C=∠C (common)
∠B=∠D=[tex]90\textdegree[/tex]
So, ΔABC ≈ ΔBCD (By AA similarity rule )
So by taking corresponding sides in ratios we get
[tex]\frac{AB}{BD}=\frac{AC}{BC}=\frac{BC}{CD}[/tex]
Now
[tex]AC.CD=BC.BC\\BC^{2} =AC.CD[/tex] -------- Eqn (1)
Similarly,
We consider ΔABD and ΔABC
∠A=∠A (Commom)
∠B=∠D=[tex]90\textdegree[/tex]
So,
ΔABD ≈ ΔABC (By AA similarity rule )
So by taking corresponding sides in ratios we get
[tex]\frac{BC}{BD}=\frac{AC}{AB}=\frac{AB}{AD}[/tex]
Now,
[tex]AB.AB=AC.AD\\AB^{2} =AC.AD[/tex] --------Eqn (2)
By Adding both the equation we get
[tex]AB^2+BC^2=AC.CD+AC.AD\\AB^2+BC^2=AC(CD+AD)\\AB^2+BC^2=AC.AC\\AB^2+BC^2=AC^2[/tex]
Hence, we proved the pythagorean theorem by using similarity of triangle.