Thread: need help for circles properties question

In the diagram,the chord AB is perpendcular to the diameter CD,AB=70cm and CE=25cm.Find
a)the radius of the circle
b)the area of triangle AOB,where O is the centre of the circle.



ans is:
a)37cm
b)420cm^2


i nid help on how to get the answer.

Originally Posted by tempq1

In the diagram,the chord AB is perpendcular to the diameter CD,AB=70cm and CE=25cm.Find
a)the radius of the circle
b)the area of triangle AOB,where O is the centre of the circle.



ans is:
a)37cm
b)420cm^2


i nid help on how to get the answer.

Have you learnt the Cartesian equation of a circle? (ie x^2 + y^2 = r^2) Or are you studying circle geometry?

Originally Posted by tempq1

In the diagram,the chord AB is perpendcular to the diameter CD,AB=70cm and CE=25cm.Find
a)the radius of the circle
b)the area of triangle AOB,where O is the centre of the circle.



ans is:
a)37cm
b)420cm^2


i nid help on how to get the answer.

Hi Tempq,

Use the property of intersecting chords AE xBE =CE xDE It's very easy then.

bjh

Hello, tempq1!

Find:

a) the radius of the circle

b) the area of

We have: .
. . and: .

Draw radius
. . Then: .

In right triangle

. .

Therefore: .



In

Therefore: .