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i got 2 tanXcos2X...dnt knw how toget furtha??

Q must b wrong

nas7232

how can you get sin2x - tanx to

2cos2x?

2cos2x?

What is the full question? to prove that they are equal?

If so: sin2x - tanx

=> 2sinxcosx - sinx/cosx

=> [2sinxcos

=> [sinx(2cos

=> tanxcos2x

Now tanx =/= cos2x so I guess I have done something wrong or the question is wrong.

samdavyson

What is the full question? to prove that they are equal?

If so: sin2x - tanx

=> 2sinxcosx - sinx/cosx

=> [2sinxcos^{2}x - sinx]/cosx

=> [sinx(2cos^{2}x - 1)]/cosx

=> tanxcos2x

Now tanx =/= cos2x so I guess I have done something wrong or the question is wrong.

If so: sin2x - tanx

=> 2sinxcosx - sinx/cosx

=> [2sinxcos

=> [sinx(2cos

=> tanxcos2x

Now tanx =/= cos2x so I guess I have done something wrong or the question is wrong.

ops sorry, that was part a) done right

part b is sin2x - tanx = 2cos2x

solve that equation

in the interval of 0<x<180

Sorry! i typed the question out wrong lol

nas7232

how can you get sin2x - tanx to

2cos2x?

2cos2x?

sin2x - tanx

= 2sincosx - sinx/cosx

= (2sinxcos^2x - sinx)/cosx

= {2sinx[(cos2x + 1)/2] - sinx}/cosx

= {sinx(cos2x + 1) - sinx}/cosx

= {sinxcos2x + sinx - sinx}/cosx

= sinxcos2x/cosx

= tanx.cos2x

So your aim was impossible.

nas7232

ah i can do it now...what a waste of thread

I still can't see how to solve it.

nas7232

ops sorry, that was part a) done right

part b is sin2x - tanx = 2cos2x

solve that equation

in the interval of 0<x<180

Sorry! i typed the question out wrong lol

part b is sin2x - tanx = 2cos2x

solve that equation

in the interval of 0<x<180

Sorry! i typed the question out wrong lol

Ahh. Thank the heavens.

sin2x - tanx = 2cos2x

=> cos2xtanx = 2cos2x

=> cos2x = 0

OR => tanx = cos2x

=> sinx/cosx = cos

=> Then what?

part b is sin2x - tanx = 2cos2x

solve that equation

in the interval of 0<x<180

as you worked out:

sin2x - tanx = tanx.cos2x

tanx.cos2x = 2cos2x

tan.cos2x - 2cos2x = 0

cos2x(tanx - 2)=0

cos2x = 0

or tanx = 2

solutions

45,63.4,135

once again, sry for not typing it out properly. Now i know why i couldn't initially do it.

solve that equation

in the interval of 0<x<180

as you worked out:

sin2x - tanx = tanx.cos2x

tanx.cos2x = 2cos2x

tan.cos2x - 2cos2x = 0

cos2x(tanx - 2)=0

cos2x = 0

or tanx = 2

solutions

45,63.4,135

once again, sry for not typing it out properly. Now i know why i couldn't initially do it.

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