# FP1 complex numbers helpWatch

#1
The last part of this question is confusing me.
the paper is edexcel june 2013 (R)
the complex number w is given by w = 10 - 5i
........
(d) given that arg(Î» + 9i + w) = Ï€/4
where
Î» is a real constant
find the value of
Î» [2]

So I have
Î» + 4i + 10 but don't know where to go from here
any help appreciated

(The mark scheme is very vague)
1
4 years ago
#2
(Original post by chloeeyay)
The last part of this question is confusing me.
the paper is edexcel june 2013 (R)
the complex number w is given by w = 10 - 5i
........
(d) given that arg(Î» + 9i + w) = Ï€/4
where
Î» is a real constant
find the value of
[FONT=Verdana]Î» [2]
1. Are you aware that you can format mathematics using latex on this site?

2. If then where can be on an Argand diagram?

3. Hence, what can you say about ? (Hint: draw a diagram)
0
4 years ago
#3
(Original post by chloeeyay)
The last part of this question is confusing me.
the paper is edexcel june 2013 (R)
the complex number w is given by w = 10 - 5i
........
(d) given that arg(Î» + 9i + w) = Ï€/4
where
Î» is a real constant
find the value of
Î» [2]

So I have
Î» + 4i + 10 but don't know where to go from here
any help appreciated

(The mark scheme is very vague)
If
0
4 years ago
#4
Arg(Î»+9i+10-5i)=pi/4
Arg(Î»+10+4i)=pi/4
Arg(z)=Arctan(imaginery part without i/Real part)
Hence, Arg(Î»+10+4i)= Arctan( 4/(10+Î»)=pi/4

Tan both sides, so 4/(10+Î»)=Tan(pi/4)
4/(10+Î»)=1 rearrange from there
1
#5
new to posting!
so.. tan theta = 4 / (
Î» + 10)
and tan(pi/4) is 1

so lambda = -6

0
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