You are Here: Home >< GCSEs

Announcements Posted on
Would YOU be put off a uni with a high crime rate? First 50 to have their say get a £5 Amazon voucher! 27-10-2016
1. Hi, I' doing an additional maths past paper and don't know how to do this five mark question:
Solve the equation 5sin2x=2cos2x in the interval 0<x<360

(the more than and less than signs should be including 0 and 360)
Thank you!
2. (Original post by xxjessietxx)
Hi, I' doing an additional maths past paper and don't know how to do this five mark question:
Solve the equation 5sin2x=2cos2x in the interval 0<x<360

(the more than and less than signs should be including 0 and 360)
Thank you!
so you know the trigonometric identity : sinx / cosx = tanx ?

use this:

divide both sides by cos2x

so 5sin2x/cos2x = 2cos2x/cos2x
5tan2x = 2
tan2x = 0.4
2x = tan^-1(0.4)
= 21.8 , 201.8, 381.8, 561.8(, 741.8) (degrees)
(because it's 2x, limit is now 720 degrees)
x = 10.9, 100.9, 190.9, 280.9(, 370.9)
because range is from 0-360 degrees, x = 10.9, 100.9, 190.9, 280.9 (degrees)

hope that helps
3. Thank you that makes sense now xxx
4. (Original post by xxjessietxx)
Thank you that makes sense now xxx
No worries How long have you been learning the content for Additional Maths?
5. I started last year but we only have one lesson a week and there's only four of us doing it

## Register

Thanks for posting! You just need to create an account in order to submit the post
1. this can't be left blank
2. this can't be left blank
3. this can't be left blank

6 characters or longer with both numbers and letters is safer

4. this can't be left empty
1. Oops, you need to agree to our Ts&Cs to register

Updated: April 17, 2016
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:
Today on TSR

Find out here

Poll
Useful resources

## Study tools

### Essay expert

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

See where you can apply with our uni match tool

### Make study resources

Create all the resources you need to get the grades.

### Create your own Study Plan

Organise all your homework and exams so you never miss another deadline.

### Resources by subject

From flashcards to mind maps; there's everything you need for all of your GCSE subjects.

### Find past papers

100s of GCSE past papers for all your subjects at your fingertips.