C3 trig help Watch

kendellex
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This is to do with trig identities. It's probably really simple but I'm having a mind block >< Name:  ImageUploadedByStudent Room1384610338.867098.jpg
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Thankyou!


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the bear
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replace tan with a well known combination of sin and cos...
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m4ths/maths247
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Whenever I teach identities I encourage all students to have a sheet which:
(1) Lists all identities and subtle manipulations
(2) Methods in which to prove identities

You have some good advice in the post above.
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kendellex
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(Original post by the bear)
replace tan with a well known combination of sin and cos...
I originally tried that and got an answer which is wrong. Name:  ImageUploadedByStudent Room1384611574.249642.jpg
Views: 154
Size:  155.9 KB


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m4ths/maths247
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(Original post by kendellex)
I originally tried that and got an answer which is wrong. Name:  ImageUploadedByStudent Room1384611574.249642.jpg
Views: 154
Size:  155.9 KB


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You didn't though

cosx/cosx = 1
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TenOfThem
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(Original post by kendellex)
I originally tried that and got an answer which is wrong. Name:  ImageUploadedByStudent Room1384611574.249642.jpg
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What did you do after the fraction line?
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username1042883
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(Original post by kendellex)
I originally tried that and got an answer which is wrong. Name:  ImageUploadedByStudent Room1384611574.249642.jpg
Views: 154
Size:  155.9 KB


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Would the last line not end up as (1+sin(2theta))/cos(2theta) ?
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kendellex
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I just multiplied it by cosx - sinx to change it out of a fraction Name:  ImageUploadedByStudent Room1384612298.602975.jpg
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TenOfThem
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(Original post by kendellex)
I just multiplied it by cosx - sinx to change it out of a fraction Name:  ImageUploadedByStudent Room1384612298.602975.jpg
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So where did your denominator go?
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m4ths/maths247
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(Original post by kendellex)
I just multiplied it by cosx - sinx to change it out of a fraction Name:  ImageUploadedByStudent Room1384612298.602975.jpg
Views: 125
Size:  163.7 KB


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But you haven't done that.

If I multiply the fraction 1/2 by 5 I dont get 5/10 I get 5/2.
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brent_
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I ended up with 1+sin theta/ 1- sin theta:confused:
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Je2
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(Original post by kendellex)
I originally tried that and got an answer which is wrong. Name:  ImageUploadedByStudent Room1384611574.249642.jpg
Views: 154
Size:  155.9 KB


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Have you been given the answer to the question?
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brent_
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1+sin theta/ 1-sin theta
then multipliying the reciprocal to the numerator
so it goes 1+sin theta (x) 1/1-sin theta
then it ended up as (1-sin theta+sin theta-sin(squared)theta)
the -sin and +sin cancels out so I was left with (1-Sin(squared)Theta) Which is cos(squared)Theta.

Is this correct? I'm doing C3 too so I need help haha
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TenOfThem
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(Original post by brent_)
1+sin theta/ 1-sin theta
then multipliying the reciprocal to the numerator
so it goes 1+sin theta (x) 1/1-sin theta
then it ended up as (1-sin theta+sin theta-sin(squared)theta)
the -sin and +sin cancels out so I was left with (1-Sin(squared)Theta) Which is cos(squared)Theta.

Is this correct? I'm doing C3 too so I need help haha
where does your \dfrac{1+\sin \theta}{1-\sin \theta}} come from
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brent_
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(Original post by TenOfThem)
where does your \dfrac{1+\sin \theta}{1-\sin \theta}} come from
I evaluated 1+sin/cos
1-sin/cos
And unfortunately ended up with that.
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TenOfThem
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(Original post by brent_)
I evaluated 1+sin/cos
1-sin/cos
And unfortunately ended up with that.
You think that \dfrac{1+\frac{\sin \theta}{\cos \theta}}{1-\frac{\sin \theta}{\cos \theta}} = \dfrac{1+\sin \theta}{1-\sin \theta}


Where did the \cos \thetas go
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Student10011
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(Original post by kendellex)
This is to do with trig identities. It's probably really simple but I'm having a mind block >< Name:  ImageUploadedByStudent Room1384610338.867098.jpg
Views: 170
Size:  129.6 KB

Thankyou!


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Is it not just tan(theta + 45)

expand it out using the double angle formulas remembering that tan(45) = 1
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TenOfThem
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(Original post by Student10011)
Is it not just tan(theta + 45)

expand it out using the double angle formulas remembering that tan(45) = 1
Yes, it is
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kendellex
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(Original post by Student10011)
Is it not just tan(theta + 45)

expand it out using the double angle formulas remembering that tan(45) = 1
Thank you! I honestly forgot that rule >< I've got it now (:

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TenOfThem
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(Original post by kendellex)
Thank you! I honestly forgot that rule >< I've got it now (:

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You may have solved this but - have you reflected on your error from earlier - do you know what you did wrong
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