Turn on thread page Beta
    • Thread Starter
    Offline

    0
    ReputationRep:
    When we have Cos(pie/2 - theta), we can represent this as Cos(-theta+pie/2)

    I understand that when drawing this graph we will shift cos(x) by pie/2 units to the left, but why is it reflected in the x axis? I thought that because it is Cos(-theta), it would be a y axis reflection, similar to y=f(-x)
    • Very Important Poster
    Online

    21
    ReputationRep:
    Very Important Poster
    (Original post by I am Babatunde)
    When we have Cos(pie/2 - theta), we can represent this as Cos(-theta+pie/2)

    I understand that when drawing this graph we will shift cos(x) by pie/2 units to the left, but why is it reflected in the x axis? I thought that because it is Cos(-theta), it would be a y axis reflection, similar to y=f(-x)
    Do you mean  cos(\frac{pi}{2} - \theta) = cos(\theta - \frac{\pi}{2}) and getting there by a transformation?
    • Thread Starter
    Offline

    0
    ReputationRep:
    No, sorry if i was a bit unclear.

    Just simply representing Cos(pi/2 - theta) graphically, which i rearranged to give cos(theta-pi/2) to make this easier to then do.
    • Thread Starter
    Offline

    0
    ReputationRep:
    (Original post by SeanFM)
    Do you mean  cos(\frac{pi}{2} - \theta) = cos(\theta - \frac{\pi}{2}) and getting there by a transformation?
    Could you kindly assist in talking me through how we represent this graphically?
    Offline

    21
    ReputationRep:
    (Original post by I am Babatunde)
    Could you kindly assist in talking me through how we represent this graphically?
    Draw a graph of cosine. What happens if you graph cosine of -theta, rather than theta? Now draw where the y axis would be for each of those functions
    • Very Important Poster
    Online

    21
    ReputationRep:
    Very Important Poster
    (Original post by I am Babatunde)
    Could you kindly assist in talking me through how we represent this graphically?
    I see, I posted to clarify as I think you've made an unfortunate typo in your OP


    I've tried to explain it but had to delete my post as to be honest it would confuse you more. It isn't easy to explain in words if you receive no further replies I will try again (will also have a think about it in the morning..)
    • Community Assistant
    Offline

    20
    ReputationRep:
    Community Assistant
    (Original post by I am Babatunde)
    When we have Cos(pie/2 - theta), we can represent this as Cos(-theta+pie/2)

    I understand that when drawing this graph we will shift cos(x) by pie/2 units to the left, but why is it reflected in the x axis? I thought that because it is Cos(-theta), it would be a y axis reflection, similar to y=f(-x)
    (Original post by I am Babatunde)
    No, sorry if i was a bit unclear.

    Just simply representing Cos(pi/2 - theta) graphically, which i rearranged to give cos(theta-pi/2) to make this easier to then do.
    I don't quite understand what your question is. It is not a translation to the left, it's a translation to the right because \cos(-x+\frac{\pi}{2})\equiv \cos(-(x-\frac{\pi}{2})) and by the even parity of the cosine function \cos(-(x-\frac{\pi}{2}))\equiv \cos(x-\frac{\pi}{2}) so really it's just a translation to the right.

    If you want to bring in reflection in the x-axis then you need to be aware that \cos(x-\frac{\pi}{2})=\sin(x) and that sine is an odd function though this is more long winded.
 
 
 
The home of Results and Clearing

3,454

people online now

1,567,000

students helped last year

University open days

  1. Bournemouth University
    Clearing Open Day Undergraduate
    Fri, 17 Aug '18
  2. University of Bolton
    Undergraduate Open Day Undergraduate
    Fri, 17 Aug '18
  3. Bishop Grosseteste University
    All Courses Undergraduate
    Fri, 17 Aug '18
Poll
A-level students - how do you feel about your results?
Help with your A-levels

All the essentials

The adventure begins mug

Student life: what to expect

What it's really like going to uni

Rosette

Essay expert

Learn to write like a pro with our ultimate essay guide.

Uni match

Uni match

Our tool will help you find the perfect course for you

Study planner

Create a study plan

Get your head around what you need to do and when with the study planner tool.

Study planner

Resources by subject

Everything from mind maps to class notes.

Hands typing

Degrees without fees

Discover more about degree-level apprenticeships.

A student doing homework

Study tips from A* students

Students who got top grades in their A-levels share their secrets

Study help links and info

Can you help? Study help unanswered threadsRules and posting guidelines

Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.