Secondary Maths questions, give me your maths questions

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mdc

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sorry, was a bit sloppy by me. should have explained that what I meant is that if the numerator is zero then the fallacy is obvious, and so the example is pointless. i.e. you only divide by (x-y) because you don't immediately realise x-y=0...if you did, you wouldn't do it.
 

treefingers

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On an Argand diagram, O is the origin and P represents the point 3 + i. The point Q
represents a + bi, where a and b are both positive. If triangle OPQ is equilateral, find a
and b.

I've tried using vectors, locus, cis etc but can't seem to get anywhere.
 

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mdc

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On an Argand diagram, O is the origin and P represents the point 3 + i. The point Q
represents a + bi, where a and b are both positive. If triangle OPQ is equilateral, find a
and b.

I've tried using vectors, locus, cis etc but can't seem to get anywhere.

Lots of ways to do this, but the most straight-forward is just to use plain old geometry:
- Draw your diagram.
- Find the angle between the Real axis and OP (let's call this x Radians).
- The angle between the Real axis and OQ is then Pi/3 + x. Draw in OQ, and hopefully you can take it from here.
 

treefingers

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Lots of ways to do this, but the most straight-forward is just to use plain old geometry:
- Draw your diagram.
- Find the angle between the Real axis and OP (let's call this x Radians).
- The angle between the Real axis and OQ is then Pi/3 + x. Draw in OQ, and hopefully you can take it from here.
It's okay, I finally figured it out :)

I had to use the formulas for sin (a+b) and cos (a+b), as the answer had to be non decimal. ended up being a =(3 - sqrt(3))/2 and b = (1+3*sqrt(3))/2
 

Hellgood

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Hey, I know it's a maths thread but does anyone here know much about physics? More specifically thermodynamics? Because I have a few problems that I just can't do.
Cheers guys.
 

mdc

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Hey, I know it's a maths thread but does anyone here know much about physics? More specifically thermodynamics? Because I have a few problems that I just can't do.
Cheers guys.

It's been a while, but if you post a couple of them I'll see if I can help.
 

Hellgood

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It's been a while, but if you post a couple of them I'll see if I can help.


Thanks mate, I'll keep this in mind for the future! I was panicking a bit, then I sat down for a couple of hours and nutted them out! Funny how things happen like that!
 

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mdc

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Q20 on combinations if anyone can solve it


Consider which combinations of 3 letters (vertices) will not form a triangle, and find the total number of these. Call this X.

Then to solve your problem, all you need is to find all possible 3-letter combinations of A-I and subtract X.
 

Subaru Impreza

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Spent a day thinking about the question eventually got it

a) 5C2 x 4C1 + 5 C1 x 4C2 = 70 (1st row choose 2 and 1 from the 2nd row) + (1 from the 1st row and 2 from the 2nd row)

b) If A was a must point ( 1C1 x 4C1 (1st row) x 4C1 (2nd row)) + (1C1 x 4C0 (1st row) x 4C2 (2nd row))= 22
 

Speck

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Question 19 , the answer is 13.4 km

Can someone explain the solution for me?

Draw a diagram like this:

25yvsm0.png


Then use the cosine rule to work out the value of x (13.4).
 

Kahuna

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Internal angles of the triangle are 40, 25, 115

from there use the sine rule. Try it yourself then I will post a solution if you are having any problems .
 

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