STEP 2 in 2024: Sharing Your Story! [PLUS WITH SOME SOLUTIONS AND PREDICTION]

Reply 80

OP

9

Original post

by vetch__

Do u guys remember for the ranges question whether the domain is Z or functions are defined on Z, meaning range is Z.

the domain is Z
if you like, you can see Q1 Q2 Q3 Q4 Q5 Q7 at https://www.xiaohongshu.com/explore/66622b64000000000d00d6f3

Reply 81

Reshjac

4

son scored a 2 in step 11 and 1 in step 3. he missed the 1 by 3 marks. He secured 4 A*s. Is there any hope, do you think?

Reply 82

mikelbird

8

Original post

by Reshjac

son scored a 2 in step 11 and 1 in step 3. he missed the 1 by 3 marks. He secured 4 A*s. Is there any hope, do you think?

The official papers and mark schemes are now available...I think the answer given for the last part of Paper 2 question3
is dodgy....surely 0<q<1 implies 0<theta<pi/2. This means that the comment at the end about an invariant point is nonsense..or am I wrong???? I im right then there are two marks here that could have made a difference to boundaries.

Reply 83

mqb2766

21

Original post

by mikelbird

The official papers and mark schemes are now available...I think the answer given for the last part of Paper 2 question3
is dodgy....surely 0<q<1 implies 0<theta<pi/2. This means that the comment at the end about an invariant point is nonsense..or am I wrong???? I im right then there are two marks here that could have made a difference to boundaries.

From a quick sketch it does seem that the question / solution has a problem. As far as I can see, you only need to really exclude 3 points from the domain so theta = 120, 150, 210 (degrees), which would make the 0<q<1 too restrictive and it doesnt contain the stated invariant point as you say.

If you exclude just those points rather than a range youd probably get 165 as another invariant point (fairly trivially/symmetry) as the composite transformation seems to be a reflection in the line at -15 degrees, which seems to be closer to what theyre asking for.

Reply 84

mikelbird

8

I think the resulting transformation is a reflection in the line y=-tanpi/12 with no invariant points

Reply 85

mikelbird

8

but theta can only be between zero and pi/2!!

Reply 86

mikelbird

8

I think this is what it looks like

Reply 87

mqb2766

21

Original post

by mikelbird

I think this is what it looks like

Pretty much agree and its a couple of lines of algebra. Personally, the question/solution reads like its been edited but not totally updated/consistent. It asks for the geometric relationship which is a reflection in the line at -15 degrees, rather than asking about invariant point(s) in the solution. The domain restriction in this part seems too restrictive to be meaningful as the previous parts simply excluded the points that map to N (which is the natural thing to do).

(edited 1 year ago)

STEP 2 in 2024: Sharing Your Story! [PLUS WITH SOME SOLUTIONS AND PREDICTION]

Quick Reply

Related discussions

Articles for you

How The Student Room is moderated