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Bloody C2 help?

The answer says I need to divide all my answers by two, but why?

(b) Solve, for 0 x < 360°,

5sin 2x = 2cos 2x,

giving your answers to 1 decimal place.(5)

Pls ignore attachment.

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(edited 8 years ago)
Reply 1
Can you link the paper?
Reply 2
Original post by fire_and_ice
Can someone work me through this Logs question from Edexcel C2 please? It's the last two parts I can't seem to do :frown:

You should have 2a - b = 1 and 2 + a + 0.5b = 1
So the second becomes a + 0.5b = -1
Multiply by 2 and then add to the first to get 4a = -1 so a = -0.25
Sub this into equation 1 to get b = -1.5
For the last partIf the log(5)x =a then 5^a=x
so x = 5^(-0.25)=0.669
using the same notation y=5^(-1.5) = 0.0894
(edited 8 years ago)
What about this question? The answer says I need to divide all my answers by two, but why?

(b) Solve, for 0 x < 360°,

5sin 2x = 2cos 2x,

giving your answers to 1 decimal place.(5)
Reply 4
Original post by fire_and_ice
Can someone work me through this Logs question from Edexcel C2 please? It's the last two parts I can't seem to do :frown:


What papers this by the way?
Original post by joe1545
What papers this by the way?


It was from a logs past question collection pack, doesn't say the year.
Original post by Tn1970
You should have 2a - b = 1 and 2 + a + 0.5b = 1
So the second becomes a + 0.5b = -1
Multiply by 2 and then add to the first to get 4a = -1 so a = -0.25
Sub this into equation 1 to get b = -1.5
For the last partIf the log(5)x =a then 5^a=x
so x = 5^(-0.25)=0.669
using the same notation y=5^(-1.5) = 0.0894


Thanks
5sin 2x = 2cos 2x.

Divide both sides by cos.

5tan2x = 2.


2x = ArcTan (2/5)

2x = 21.8, 201.8, 381.8, 561.8. (It's 2x so you double the interval.)

x = 10.9, 100.9, 190.9, 208.9

Caution: I've been doing physics, stats and FP2 all morning so the values might be wrong, but the method should work.
Original post by fire_and_ice
What about this question? The answer says I need to divide all my answers by two, but why?

(b) Solve, for 0 x < 360°,

5sin 2x = 2cos 2x,

giving your answers to 1 decimal place.(5)


Because it's 2x not just x
So since you are to find x, you divide the answer you get with 2x by 2.
So if you get e.g
2x=y
Then, x=y/2
Ya dig?
Soz I'm not very good at explaining maths. Hope that helped. :biggrin:

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