How is the angle bisector created in the diagram?

The given explanation is: Let O be the center of the smaller circle. The lines CO and DA are parallel (both perpendicular to DB). Consequently, the angles DAB and COB are equal.

Now in the small circle the angle CAO divides a chord, the angle of which at the corresponding center is called COB.

Consequently: CAO = 1/2 COB = 1/2 DAB.

Thus CAO = DAC: AC is then the angle bisector of DAB.

It's precisely the "consequently" that I don't understand. Does anyone have a plausible explanation?

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gauss58
1 year ago

Triangle OAC is equal

Angle CAO = angle OCA

Angle COB = external angle to triangle OAC

Angle COB = angle DAB = angle CAO + angle OCA

Willy1729
1 year ago

Hello,

From C, take a tendon of the small circle to the point at which the small circle and the diameter of the large circle AB intersect.

Name this intersection E.

Then the peripheral angle set is valid in the small circle.

The center angle EOC is twice as large as the periphery angle EAC over the same chord CE.

Since EOC=BAD, the assertion is correct.

Best regards,

Willy

Willy1729
1 year ago
Reply to  SchakKlusoh

The other intersection. The diameter cuts the small circle not only at one point.