Non-existant circle property that should be true (1 Viewer)

[miegoreng]

The property "equal arcs subtend equal angles at the circumference" is true but "equal chords subtend equal angles at the circumference" is not true.

Equal arcs subtend equal chords so why isn't the second property true?

 

[YannY]

You gotta understand that having a chord subtending an angle to the circumference gives you a variable angle. unless of course its the diameter.

 

[vds700]

im just looking at the excel guide for ext 1 and it has the property "Equal angles at the centre stand on equal chords". We know that the angle at the centre is twice the angle at the circumference. So if the angles subrtended by the chords at the centre are the same, then the angle subtended by the chords at the circumference must also be the same surely? So your second property is true.

 

[foram]

If a chord subtends an angle, then it's the same as having the arc subtend the angle isn't it? Because the chord touches the arc at the place they both subtend the angle? isn't that right? My math teacher said that the equal arcs subtends equall angles could also be called equal chords subtend equall angles at the circumference...

 

[undalay]

is this wat it means?

 

[miegoreng]

Ahhh I get it. Thanks undalay, your picture made things heaps clearer.
Its hard to explain but basically chords with angles at the cirumference can go back into the small part of the cirlce but arcs can't go back as they are already the edge.

 

[YannY]

If a chord subtends an angle, then it's the same as having the arc subtend the angle isn't it? Because the chord touches the arc at the place they both subtend the angle? isn't that right? My math teacher said that the equal arcs subtends equall angles could also be called equal chords subtend equall angles at the circumference...

THeres one person in your school thats smart? and thats you? what about me man? im doing 4u maths 4u english + modern and i came first in everything.

So really ... you're not that smart after all failing english... TSKTSK :rofl:

 

[keithkung]

Ahhh I get it. Thanks undalay, your picture made things heaps clearer.
Its hard to explain but basically chords with angles at the cirumference can go back into the small part of the cirlce but arcs can't go back as they are already the edge.

In other words, for chords the angle they substend must be in the same segment, which is covered by the reference "angles substeded by the same chord in the same segment is equal" already.