x Turn on thread page Beta
 You are Here: Home >< Maths

# trig help image provided watch

1. all information in the picture thanks for you help!
all information in the picture thanks for you help!
Sketch a sin graph and you'll see
Hint: sin(x) = 0

You have two equations to solve from your question which you have correctly identified. sin(x)=0 and cos(x)=-sqrt(3)/2. We are, however, missing the interval for the results because there are an infinite number of solutions without one. What is the exact question?

Let's start with sin(x). You should know what the curve looks like, but here

So where on this is sin(x) 0?

Now for the cos(x) graph:

Notice how it's symmetrical in the Y-axis, meaning that cos(x)=cos(-x) so if you solve cos(x)=-sqrt(3)/2 and get an answer you also have the negative value of that as an answer.

Tom
4. (Original post by tom982)

You have two equations to solve from your question which you have correctly identified. sin(x)=0 and cos(x)=-sqrt(3)/2. We are, however, missing the interval for the results because there are an infinite number of solutions without one. What is the exact question?

Let's start with sin(x). You should know what the curve looks like, but here

So where on this is sin(x) 0?

Now for the cos(x) graph:

Notice how it's symmetrical in the Y-axis, meaning that cos(x)=cos(-x) so if you solve cos(x)=-sqrt(3)/2 and get an answer you also have the negative value of that as an answer.

Tom
brilliant response tom, thank you

but how do we get the 180?
5. how do we get the 180?

thanks
how do we get the 180?

thanks
By opening your eyes, and using the graphical answers people have given you.

Sin(x)=0

At 180, according the diagram people just posted. If you followed the curve back to the negative axis, you can see at -90, it'll be -1, and at -180 it'll be 0. Hence your +- 180 values.

Now, Cos(x)=-root(3)/2 is 150. Look at the diagrams provided. Cos is symmetrical about the y axis, thus -150 is also the same.

You could however recall that to gain other solutions, in the case of Sin(x) is 180-x, and for Cos(x) is 360-x.

So infact, 360-150 is also a value, 210.

As Cos(210) = -root(3)/2.

And this therefore means due to symmetry that, -210 is also a value.
how do we get the 180?

thanks
Again, looking at the sine curve:

Since we are solving for sin(x)=0, we are looking for values of X when Y=0, so one way to look at this is to think where does this cross the X axis? There are infinitely many, as I previously said, but just tell me the ones in that image for teaching purposes.

Tom

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: March 9, 2013
Today on TSR

### Happy St Patrick's day!

How are you celebrating?

### Stay at sixth form or go to college?

Discussions on TSR

• Latest
Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest

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