You are Here: Home >< Maths

# trig identites come help please i dont get how you do the end bit always mesup on end watch

1. i get everything else just the end but i get half of it wrong like in the attachment i dont understand the reading that you get could someone please explain to me thanx people
also the point im stuck is were the arrow is pointing at
Attached Images

2. Do you mean when you are trying to take a Trig Identity from a Sine/Cosine/Tan graph?
3. what attachment?
4. (Original post by Steevee)
Do you mean when you are trying to take a Trig Identity from a Sine/Cosine/Tan graph?
yes boss like u see at the end when they get the angles that you need to get to the angle that there is on the graph basically on the picture where my arrow is pointing to thats the part i dont get thanx
5. (Original post by roar558)
what attachment?
cant you see any attachment i seriously attached it
6. (Original post by ketchup)
cant you see any attachment i seriously attached it
no I can't see any attachment? maybe try posting it again?
7. (Original post by roar558)
no I can't see any attachment? maybe try posting it again?
lol i editedit 3rd time isit up now?lol
8. (Original post by ketchup)
lol i editedit 3rd time isit up now?lol
Yeah it's up now, if you are referring to the -117, they've just rounded the -116.6 to 3 sig figs
9. (Original post by roar558)
Yeah it's up now, if you are referring to the -117, they've just rounded the -116.6 to 3 sig figs
i get how u get that and the 63.4 aswell but i dont get how they get the 180's
10. (Original post by ketchup)
i get how u get that and the 63.4 aswell but i dont get how they get the 180's
Look at the line above the one your arrow points to. It has two sets of solutions, one set is the set of solutions to , which is where the 180s and 0 come from; the other is the set of solutions to . All the line the arrow points to has done is combine the two sets of solutions into one set and written them in ascending order.
11. (Original post by ketchup)
i get how u get that and the 63.4 aswell but i dont get how they get the 180's
the tan graph repeats itself every 180 degrees so as tan^-1(0)=0, it also =180 and -180.
12. thanx i see people thanx for the help everyone
13. basically

if it's tan, just +/- 180 to the value to get what ever range you want

then if it is cos, you do 360 - alpha ---> lets say cos(theta = 0.5, then theta = 60. Now use 360 - theta = 300. We now have the two definite value in the common 0 - 360 degree range, these values were 60 and 300, right? now you can keep adding and subtracting 360 to get the value in what ever range you like

same thing with sin, but this time 180 - theta. get your theta value, 180 - theta, we have two definite values in the 0 - 360 range, now +/- 360 to get values in what ever range etc

tan was the funny one, you only solve it for 1 definite value, then you can +/- 180 to get what ever range you want

I call it a definite value because it's directly derived from the equation

it's useful to understand this graphically too

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: April 12, 2011
Today on TSR

### Medicine offers

Find out which unis send them quickest

### University open days

• Sheffield Hallam University
Wed, 17 Oct '18
• Staffordshire University
Wed, 17 Oct '18
• Teesside University
Wed, 17 Oct '18
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

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