Prove that Sin squared theta + Cos squared theta is equal to 1

We know that;
Sin theta=Perpendicular/Hypotenuse=P/H=a/c
Cos theta=Base/Hypotenuse=B/H=b/c
So, Sin^2 theta+Cos^2 theta=a^2/c^2+b^2/c^2=a^2+b^2/c^2 …….(i)
By Pythagoras Theorem, in a right-angled triangle:
Hypotenuse^2=Base^2+Perpendicular^2
c^2=a^2+b^2
1=a^2+b^2/c^2………(ii)
Put eq. (ii) in eq. (i), we get
Sin^2 theta+Cos^2 theta = 1
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