Year 12s: what will be the first way you research your future options? >>

Maths Trig Question

RedDevils

Prove that

1 + sin x
cos x

is equal to

cos x
1 - sin x

Reply 1

m:)ckel

In the answer, you see a (1-sinx) at the bottom, so does that give you any clues on how should go about it?

Reply 2

IChem

remember that

cos^2x + sin^2x = 1

That's all you need to know.

Reply 3

Bilek

extend (1+sinx)/cosx = (1+sinx)(1-sinx)/cosx(1-sinx) = 1-sin^2x/cosx(1-sinx)=cos^2x/cosx(1-sinx)=cosx/1-sinx .... and we're home :wink:

Reply 4

ColinOfEdinburgh

Bilek

extend (1+sinx)/cosx = (1+sinx)(1-sinx)/cosx(1-sinx) = 1-sin^2x/cosx(1-sinx)=cos^2x/cosx(1-sinx)=cosx/1-sinx .... and we're home :wink:

Well that takes the challenge away for them :rolleyes:

Reply 5

IChem

Bilek

extend (1+sinx)/cosx = (1+sinx)(1-sinx)/cosx(1-sinx) = 1-sin^2x/cosx(1-sinx)=cos^2x/cosx(1-sinx)=cosx/1-sinx .... and we're home :wink:

It's simpler to square, rearrange and then root....

Reply 6

RedDevils

oh yeah of course, thanks everyone i did them all but this one and just couldn't see what i was supposed to do lol.

Reply 7

Bilek

IChem

It's simpler to square, rearrange and then root....

All paths are good if they aim for the destination :wink:

indeed

IChem

It's simpler to square, rearrange and then root....

If you want simple methods, surely it's much easier to start off from cos²(x)+sin²(x)=1, DOTS, and cross divide? Though perhaps not quite as easy to spot.

ColinOfEdinburgh

Well that takes the challenge away for them :rolleyes:

Exactly.

Bilek

extend (1+sinx)/cosx = (1+sinx)(1-sinx)/cosx(1-sinx) = 1-sin^2x/cosx(1-sinx)=cos^2x/cosx(1-sinx)=cosx/1-sinx .... and we're home :wink:

Please see this thread. The general concensus reached was that full solutions should not be given unless specfically asked for, or the OP has been struggling for a long time (with hints) and still hasn't got it. The "ruling" by one of the mods is below:

insparato

So my ruling is please try and refrain from giving full solutions unless the OP after lots of help still hasn't grasped it. Might me a nice little thing to do when providing help is to tell the OP that if they do need more help or haven't understood something all they have to do is ask. I've read through all the 6 pages and i still stand by it as the best way to support peoples learning.