The Student Room Group

C3 Trigonometry - Where did I go wrong?

Reply 1
Original post by ps1265A
...

For the tan/sec question, +3+\sqrt{3} in the first line has changed to 3-\sqrt{3} in the second line.

For the other question, your working on the right of your page is fine up until the last line where you wrote sinθ=53\sin \theta = \frac{5}{3} instead of the correct version : sinθ=35\sin \theta = \frac{3}{5}.
(edited 9 years ago)
Reply 2
Original post by arkanm
From the first line to the second, you did:

" sec2θ(1+3)tanθ+3=1\sec^2 \theta -(1+\sqrt{3})\tan \theta +\sqrt{3}=1

sec2θ[tanθ+3+3tanθ+3]=1\sec^2 \theta-\left [\tan \theta+\sqrt{3}+\sqrt{3}\tan \theta +3\right ] = 1 "

When it should have been:

" sec2θ(1+3)tanθ+3=1\sec^2 \theta -(1+\sqrt{3})\tan \theta +\sqrt{3}=1

sec2θ[tanθ+3tanθ3]=1 \sec^2\theta - \left[\tan \theta + \sqrt{3} \tan \theta - \sqrt{3}\right] =1 "


I still don't see how you've formed a "-" square root 3
Reply 3
How do you guys type sin tan cos theta like that?
Hi!

Firstly, this should help with regards to typing mathematical notation using LaTeX on TSR. http://www.thestudentroom.co.uk/wiki/LaTex

Re: 5cosθ=3cotθ5 \cos \theta = 3 \cot \theta
notnek is right, sinθ=35\sin \theta = \frac{3}{5} (not 5/3) is the only correction that needs to be made.

Re: other question, don't multiply anything out - just keep it simple!

Hints:
1) Use the formula sec2θ=1+tan2θ\sec^2 \theta=1+ \tan^2 \theta.
2) Cancel the 1 from both sides.
3) Solve the quadratic equation for tanθ\tan \theta.
4) Use calculator to arctan the two roots.

Hope this helps. The final answers are nice! :smile:

Quick Reply

Latest