You are Here: Home >< Maths

# C3/C4 Trig

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 asked this question a couple of weeks ago but the replys wont come up so im asking again)

A 2 mark question in a c3 paper:
solve
arcsinX=arccosX

i have made the subtitution arccosx=y so x=cosy but im kind of stuck after this

(it is INCORRECT to assume sinx=cosx)

Thanks
2. OK so
arcsinx=arccosx
arccosx=y
cosy=x
arcsinx=y
siny=x
now REMEMBER cos(Θ)=sin(π/2-Θ)
so cosy=sin(π/2-y)
x=sin(π/2-y)
arcsinx=π/2-y (arcsinx=y)
y=π/2-y
2y=π/2
y=π/4
sinπ/4=x=1/root2
substitute this answer into each side of the equation and you should get the same answer

## 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: June 14, 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

### University open days

Is it worth going? Find out here

Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read here first

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams