# Dat circle geo (1 Viewer)

#### RealiseNothing

##### what is that?It is Cowpea
Was the sneakiest thing ever.

#### bunnypacman

##### Member
Are you talking about 13d) ?

#### lolcatss

##### New Member
How was it sneaky?

#### RealiseNothing

##### what is that?It is Cowpea
How was it sneaky?
Most of the "obvious" proofs would be invalid.

A lot of people would have assumed it was a straight line and done alternate angles.

#### Focus is Key

##### Member
Most of the "obvious" proofs would be invalid.

A lot of people would have assumed it was a straight line and done alternate angles.
Damn!!!!!!!!!!!!!!!!!!!! I did that

#### j1mmy_

##### Member
Most of the "obvious" proofs would be invalid.

A lot of people would have assumed it was a straight line and done alternate angles.

Oh crap

#### Magical Kebab

##### Member
Most of the "obvious" proofs would be invalid.

A lot of people would have assumed it was a straight line and done alternate angles.
I did that whilst knowing it was wrong coz I had no other method of doing it lol

#### bunnypacman

##### Member
What was the solution?? ><

#### andrew29223

##### New Member
Draw a tangent through the point of intersection, then use angle in alternate segment theorem and vertically opposite angles (angles between the line you are given and your tangent) and prove the two alternate angles are equal therefore must be collinear

#### lulwut

##### New Member
if you did alternate angles from the tangent drawn between the two circles, the proof would be valid right? you're proving that both angles produced from the tangent to their respective lines are equal -> therefore lies on the same line / co-linear.. I think..

#### RealiseNothing

##### what is that?It is Cowpea
Draw a tangent through the point of intersection, then use angle in alternate segment theorem and vertically opposite angles (angles between the line you are given and your tangent) and prove the two alternate angles are equal therefore must be collinear
This is what I did.

#### lulwut

##### New Member
Draw a tangent through the point of intersection, then use angle in alternate segment theorem and vertically opposite angles (angles between the line you are given and your tangent) and prove the two alternate angles are equal therefore must be collinear
I'm always late to the party :'(

#### RealiseNothing

##### what is that?It is Cowpea
if you did alternate angles from the tangent drawn between the two circles, the proof would be valid right? you're proving that both angles produced from the tangent to their respective lines are equal -> therefore lies on the same line / co-linear.. I think..
I think that's fine.

#### panda15

##### Alligator Navigator
Draw a tangent through the point of intersection, then use angle in alternate segment theorem and vertically opposite angles (angles between the line you are given and your tangent) and prove the two alternate angles are equal therefore must be collinear
I did this. Glad I'm not the only one.

#### ninasandwich

##### New Member
yeah... I think I screwed this question up completely- I might scab a mark for it but- I saw I couldn't assume so I forgot about that proof, and instead went with the one that claims "any 3 non-collinear points are con-cyclical points" , then stated as point T is the point of intersection, a line drawn between the centres of the circles passes through T. Therefore since 'Q' and 'P' are points on the circumference of their respective circles, the three points cannot form a circle, and therefore must be collinear. hahah I hope they give me mark for trying

#### seanieg89

##### Well-Known Member
Was the sneakiest thing ever.
Is there a copy of the paper or question uploaded anywhere?

#### iBibah

##### Well-Known Member
Is there a copy of the paper or question uploaded anywhere?

Prove Q T and P are collinear.

#### RealiseNothing

##### what is that?It is Cowpea
Hey iBibah, doesn't it remind you of the UNSW seminar back in January.

Where like EVERYONE, including the 3rd year maths students, assumed it was a straight line.

de ja vu

#### seanieg89

##### Well-Known Member
Hey iBibah, doesn't it remind you of the UNSW seminar back in January.

Where like EVERYONE, including the 3rd year maths students, assumed it was a straight line.

de ja vu
Lol, that's why you should choose usyd .