# Does Q6 (a) miss anything? (1 Viewer)

#### stears

##### Space Monkey
How did u do the Q6 (a) (i), the question didn't give any angle

#### withoutaface

Proof is as follows:

ABD=ACD(angles subtended from the same chord)
:. FBD=FCA (angles on a straight line are supplementary)
But FBD+FCA=180 (opposite angles of a cyclic quad are supplementary)
:. FDB=180/2=90

#### acmilan

##### I'll stab ya
that would make AD the diameter and hence AD = 2r. Am i right?

#### skypryn

##### sexual robot
in those types of q's you have to be smart....it is normally 90, 180, 60 etc cos you can cancel <'s

#### withoutaface

acmilan1987 said:
that would make AD the diameter and hence AD = 2r. Am i right?
Yeah<etcetc>

#### absolution*

##### ymyum
I got those answers but didnt gave a really retarded proof coz i knew by looking at it it was a right angle.
Then i just wrote that the line was = 2r. pure guess. I hope i get marks.

#### derek_

##### Member
Rofl Your Meant To Get An Angle??? =(~

#### mazza_728

##### Manda xoxo
I didnt get the first part at all.. didnt have time to figure it all out but i guessed the 2nd part to be 2r do u think ill still get it???

#### susukira

##### New Member
the diagram was jus fucked

#### withoutaface

susukira said:
the diagram was jus fucked
What makes you say that?

#### CharlieB

##### ?uestlove
the question was pretty straightforward...

they told you the other quad was cyclic so it obviouslt involved the exterior angle thing

#### sub

##### Member
i got it right!! YAY!

#### dawso

##### needmorecustomstatusspace
yeah, this question was actually heaps easy, if u got the question rite....

(dumbass me first didnt read the question 2 see wat was given as the cyclic quadrilateral and i was workin out the value of the wrong angle)

so theres a tip peoples, read the question!!!!

#### mr phil

##### New Member
yea i fudged that question aswell.. shouldve read the whole thing.. coz i assumed the cyclic quad was the one in the diagram, (the one with a circle around it!)
i said let sum angle = a, let the other one = b, so whatevvr angle = a +b
any chance at one out of the 2 marks?!

second part AD = rM, where M is a variable ? doubt that'd get the one mark

#### Li0n

##### spiKu
lol dude i did everything in algebra.
i didnt know you could assume that AD was diameter. for ii i go
Construct DX such that DX is a diameter of the circle
then i go DX = (2r)<sup>2</sup> = pythagoras bla.

#### bevstarrunner

##### Maths Nut
you can say that AD is the diameter when you prove either < ABD or < ACD to be 90º. Then you can say it is diameter because AD subtends the right angle at the circumference.

#### beverly

##### Member
argh..i knew i shouldve guessed it. i came out of the exam thinking..i shouldve just guessed 90 and 2r cos' that's the only logical answer

##### B4nn3d
It's a 1 marker, for the length of the line to be a simple function of r, the angle must be 90 degrees. Man, answer by inspection is so so much easier than actually doing anything.

#### ~*HSC 4 life*~

##### Active Member
derek_ said:
Rofl Your Meant To Get An Angle??? =(~
lol!!

hey i got it right...but my reasoning was pretty wrong, gonna lose marks for that

#### Komaticom

##### Bored Member
Damn diagram, so misleading. They drew angles so wrong. How can two opposite angles of a cyclic quad add to equal 180 when they're drawn to be both obtuse... *grumble grumble * "not to scale" *grumble grumble*