Thread: basic circle geometry

Hi all,

, tangent is perpendicular to radius at point of contact

, angle sum of triangle is 180, triangle OAB is isosceles (equal angles opposite equal sides)



, angle sum triangle is 180

BUT....

Angle sum of quadrilateral is

In which case





is this a poorly drawn up question or is the reasoning flawed?

thanks.

Originally Posted by sammy28

Hi all,

, tangent is perpendicular to radius at point of contact

, angle sum of triangle is 180, triangle OAB is isosceles (equal angles opposite equal sides)



, angle sum triangle is 180

BUT....

Angle sum of quadrilateral is

In which case





is this a poorly drawn up question or is the reasoning flawed?

thanks.

What you've calculated is the angle indicated in red.

Subtract the base angle of the isosceles triangle and you'll get your first result.

thanks earboth. i should pay more attention