OK for some strange reason, this some isn't working out

Test Preparation
1

<p>no clue why I can't do thiss, seems straightforward enough...</p>

<p>y=[(1-sin2x)/(1+sin2x)]^0.5</p>

<p>Prove that dy/dx + [sec(pi/4-x)]^2 = 0</p>

<p>Can anyone help please?</p>

<p>Thanks :)</p>

2

<p>bump.</p>

<p>sorry people, I know this is AP time but this is KILLING me! :(</p>

3

<p>sorry about the title of the thread, I was distracted :o</p>

4

<p>bump :(</p>

5

<p><em>resolutely bumps thread up</em></p>

6

<p>Take the derivative and simplify a little bit then you'll get
dy/dx = -2cos2x/[(1-sin2x)^(1/2) (1+sin2x)^(3/2)]
= -2cos2x/[(1+sin2x)(1-(sin2x)^2)^(1/2)]
= -2/(1+sin2x)</p>

<p>sec(pi/4-x)^2 = 1/cos(pi/4-x)^2
= 1/(cosx/sqrt(2) + sinx/sqrt(2))^2
= 2/(cosx+sinx)^2
= 2/(1+sin2x)</p>

<p>so dy/dx + sec(pi/4-x)^2 = 0</p>