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secondary 4 | A Maths
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CIA
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secondary 4 chevron_right A Maths chevron_right Singapore

How to work out the steps part ii ? Tks

Date Posted: 2 years ago
Views: 458
Eric Nicholas K
Eric Nicholas K
2 years ago
So for part ii, we reflect Q along line AB to get an "image" R.

The shortest distance between P and R is the straight line joining them (i.e. the straight line PR).

But PR = PC + CR and then it's pretty obvious that CR = CQ. so this leads to PR = PC + CQ being the shortest.

From here, triangles PAC and RBC are similar
- angles PAC and RBC are right angles
- angles PCA and RCB are vertically opposite each other

The length ratio PA : RB is 10 : 15, which simplifies to 2 : 3.

Correspondingly, AC : BC = 2 : 3 as well due to the similarity of both triangles.

So, AC : AB = 2 : 5, and AC = 2/5 x 20 = 8 km.

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Jk
Jk's answer
18 answers (Tutor Details)
1st
Jk
Jk
2 years ago
lemme know if its right~
CIA
CIA
2 years ago
Part i is correct , how about part ii? Tks
Eric Nicholas K
Eric Nicholas K
2 years ago
The shortest distance between two points is basically a line joining two points.

You need an idea like this for part ii.
CIA
CIA
2 years ago
Kindly present the workings part ii, tks
Eric Nicholas K
Eric Nicholas K
2 years ago
Will be letting someone else present this as I don’t have time to write for the moment. If I can remember at night (~ 2 am) or over the next few days, I will write down my workings.

Part ii’s workings uses similar triangles.
Eric Nicholas K
Eric Nicholas K
2 years ago
Added to the main chat's text box.