B
go
2dB
A a
sad
Cta
ca
C
1. Angle subtended by a diameter of a circle is
always 90. Thales’ Theorem
2. Suppose angle OAB is a .
3. We know that angle OBC is also equal to 90
after some trig properties.
4. The it implies that angle BCO is equal to angle
ABO
5. That it follow that their tangle are equal and the
proof follow