Plutoniummatt
Badges: 0
Rep:
?
#1
Report Thread starter 11 years ago
#1
Hiya Mathematicians!

Could someone fill out the missing steps for me please thanks.

16\cos^2 \theta

into

8(\cos 2\theta + 1)

I've done it before but can't do it now, just one of those days :s Thanks
0
reply
Glutamic Acid
Badges: 16
#2
Report 11 years ago
#2
\cos(2 \theta) = 2 \cos^2 \theta - 1. Rearrange this.
0
reply
IChem
Badges: 11
Rep:
?
#3
Report 11 years ago
#3
(Original post by Plutoniummatt)
Hiya Mathematicians!

Could someone fill out the missing steps for me please thanks.

16\cos^2 \theta

into

8(\cos 2\theta + 1)

I've done it before but can't do it now, just one of those days :s Thanks
\cos^2 \theta - \sin^2 \theta = \cos 2 \theta

\cos 2 \theta = 2 \cos^2 \theta -1

Now rearrange...
0
reply
Plutoniummatt
Badges: 0
Rep:
?
#4
Report Thread starter 11 years ago
#4
cheers guys....
0
reply
nota bene
Badges: 13
Rep:
?
#5
Report 11 years ago
#5
cos(2t)=cos^2(t)-sin^2(t) so 8cos(2t)=8c^2-8s^2 and 8=8c^2+8s^2
0
reply
qgujxj39
Badges: 15
#6
Report 11 years ago
#6
Start with \cos(A + B) = \cos A \cos B - \sin A \sin B
Spoiler:
Show
Let A = B = \theta so you have \cos 2 \theta = \cos^2 \theta - \sin^2 \theta
Using \sin^2 \theta = 1 - \cos^2 \theta you get
\cos 2 \theta = 2 \cos^2 \theta - 1
and thus
2 \cos^2 \theta = \cos 2 \theta + 1
multiply both sides by 8 et voila.
0
reply
qgujxj39
Badges: 15
#7
Report 11 years ago
#7
How sad is that, it's 10 past midnight and 4 of us lot replied within two minutes.
0
reply
Glutamic Acid
Badges: 16
#8
Report 11 years ago
#8
It's Saturday night and ... I'm doing maths.
0
reply
Audrey Hepburn
Badges: 12
Rep:
?
#9
Report 11 years ago
#9
(Original post by Glutamic Acid)
It's Saturday night and ... I'm doing maths.
I'm working through the vectors chapter in my FP3 book :cool:
0
reply
Plutoniummatt
Badges: 0
Rep:
?
#10
Report Thread starter 11 years ago
#10
it's sunday morning and FP3 is tomorrow, for AQA anyways I just got back form pub....rofl prolly why i couldnt even convert a bit of trig
0
reply
IChem
Badges: 11
Rep:
?
#11
Report 11 years ago
#11
Hehe, not until Friday for me, FP1 is 2moz!
0
reply
qgujxj39
Badges: 15
#12
Report 11 years ago
#12
(Original post by Glutamic Acid)
It's Saturday night and ... I'm doing maths.
Surprisingly enough, I'm not. I was doing some FP1 about an hour ago, though.
0
reply
qgujxj39
Badges: 15
#13
Report 11 years ago
#13
(Original post by IChem)
Hehe, not until Friday for me, FP1 is 2moz!
****, it's tomorrow now isn't it! :eek: well it's afternoon, so can afford a bit of a lie-in, which is always good.
0
reply
Plutoniummatt
Badges: 0
Rep:
?
#14
Report Thread starter 11 years ago
#14
i got sunday (today) off work to do FP3....-.- lol, plus i got the big synoptic phyisics paper on tuesday
0
reply
Audrey Hepburn
Badges: 12
Rep:
?
#15
Report 11 years ago
#15
(Original post by Plutoniummatt)
it's sunday morning and FP3 is tomorrow, for AQA anyways I just got back form pub....rofl prolly why i couldnt even convert a bit of trig
Edexcel for the win!
0
reply
HeatherChandler
Badges: 0
Rep:
?
#16
Report 11 years ago
#16
(Original post by tommmmmmmmmm)
How sad is that, it's 10 past midnight and 4 of us lot replied within two minutes.
Yeah we should totally all kill ourselves.
0
reply
Plutoniummatt
Badges: 0
Rep:
?
#17
Report Thread starter 11 years ago
#17
(Original post by Audrey Hepburn)
Edexcel for the win!

Edexcel don't give many past papers or mark schemes for my physics course
0
reply
Audrey Hepburn
Badges: 12
Rep:
?
#18
Report 11 years ago
#18
(Original post by Plutoniummatt)
Edexcel don't give many past papers or mark schemes for my physics course
Not for Physics - AQA for the win for Physics :proud:
0
reply
Plutoniummatt
Badges: 0
Rep:
?
#19
Report Thread starter 11 years ago
#19
(Original post by Audrey Hepburn)
Not for Physics - AQA for the win for Physics :proud:
Damn my school :mad:
0
reply
X

Quick Reply

Attached files
Write a reply...
Reply
new posts
Back
to top
Latest
My Feed

See more of what you like on
The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

Personalise

University open days

  • University of Bristol
    Undergraduate Open Afternoon Undergraduate
    Wed, 23 Oct '19
  • University of Exeter
    Undergraduate Open Day - Penryn Campus Undergraduate
    Wed, 23 Oct '19
  • University of Nottingham
    Mini Open Day Undergraduate
    Wed, 23 Oct '19

Have you made up your mind on your five uni choices?

Yes I know where I'm applying (138)
61.61%
No I haven't decided yet (50)
22.32%
Yes but I might change my mind (36)
16.07%

Watched Threads

View All