Assuming angles in diagrams. (1 Viewer)

[Meldrum]

Aftger looking through a fair few past HSC exams, it seems the norm to assume the size of certain angles. For those playing at home, last year's Q3 (c) had 2 assumed angles.

Now, I've been taught for a long time that just because it may look 90* or 180*, doesn't mean that it is. So, my question is: Can we assume that an angle is a certain magnitude based purely on a diagram?

Thanks.

Gav.

 

[acmilan]

You are assuming the N is due north of P, hence RPQ = 20. I guess you shouldnt but considering its only question 3 i think the assumption would be safe. In worst case scenarios, you can always indicate to the examiners that there is a problem But you're right, generally you should assume anything without reasons

 

[Meldrum]

That was just one type. The other was that NRP was 90*...can we assume right angles?

 

[Slidey]

Generally not.

ESPECIALLY NOT if they say "diagram not to scale"

 

[acmilan]

That was just one type. The other was that NRP was 90*...can we assume right angles?

err you lost me, why are you assuming NRP is 90?

 

[Meldrum]

lol. Sorry NPQ.

The answer assumes that it is 90*.

 

[acmilan]

lol. Sorry NPQ.

The answer assumes that it is 90*.

Yeah that follows from the assumption that N is due north of P. And since Q is due east of P (which was given), when east meets north, you get a right angle

 

[Meldrum]

Sorry, stupidity.

I really should get some sleep after 48 hours of gaming...blegh.

 

[acmilan]

Now that I look at it, the arrow at N probably shows they expect you to assume that N is due north. If thats the case then there are no assumptions at all in the question. However its still a crap question that they should have properly stated that N is due north.