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Mathematics 14 Online
OpenStudy (anonymous):

Trigonometry help?

OpenStudy (anonymous):

@Nnesha \[\frac{ \cos \theta }{ 1-\sin \theta } + \frac{ 1-\sin \theta }{ \cos \theta }\]

Nnesha (nnesha):

i love that type of question that is equal to what there should be an equal sign

OpenStudy (anonymous):

sorry, it's just simplify :)

Nnesha (nnesha):

find common denominator

OpenStudy (anonymous):

\[\cos \theta(1-\sin \theta)\]

Nnesha (nnesha):

right when we find common denominator we should multiply the numerator of 1st fraction by the denominator of 2nd fraction multiply numerator of 2nd fraction by the denominator of 1st fraction \[\frac{ \cos \theta }{\color{Red}{ 1-\sin \theta} } + \frac{ 1-\sin \theta }{\color{blue}{ \cos \theta} }\] \[\frac{ \color{blue}{\cos \theta}*\cos \theta + \color{Red}{(1-\sin \theta)}(1-\sin \theta) }{ \cos \theta(1-\sin \theta) }\]

Nnesha (nnesha):

simplify that.

OpenStudy (anonymous):

wouldn't that be \[\cos \theta + (1-\sin \theta)\]

OpenStudy (anonymous):

I don't know how else to simplify that...

Nnesha (nnesha):

did you get this cos theta+ (1-sinx) after simplifying ? and are you sure it's (1 `-` sinx) at the numerator and denominator im just guessing one of them supposed to be positive (1+sinx)

OpenStudy (anonymous):

one of the cos thetas and one of the (1-sin theta)s should cancel, right? That leaves cos theta + (1-sin theta), doesn't it?

Nnesha (nnesha):

No0o0o!!! you can't do that

Nnesha (nnesha):

\[\frac{ \color{blue}{\cancel{\cos \theta}}*\cos \theta + \color{Red}{\cancel{(1-\sin \theta)}}(1-\sin \theta) }{ \cancel{\cos} \theta\cancel{(1-\sin \theta)} }\] This is NOT allowed. bec that's same as \[\rm \frac{ \cos \theta*\cos \theta }{ \cos(1-\sin \theta) } +\frac{(1-\sin \theta)(1-\sin \theta)}{\cos \theta(1-\sin \theta)}\]

Nnesha (nnesha):

both term at numerator are dividing by cos theta (1-sin theta)

Nnesha (nnesha):

|dw:1445992109060:dw| that' would be the next step

Nnesha (nnesha):

make sense ?? :=))

OpenStudy (anonymous):

\[\frac{ \cos^2\theta+\sin^2\theta-2\sin \theta + 1 }{ \cos \theta(1-\sin \theta) }\]

Nnesha (nnesha):

looks good now use the identity \[\rm \cos^2 \theta + \sin^2 \theta =1 \] solve this for cos^2

Nnesha (nnesha):

\[\frac{ \color{Red}{\cos^2\theta}+\sin^2\theta-2\sin \theta + 1 }{ \cos \theta(1-\sin \theta) }\] cos^2 theta = ??? use the identity

OpenStudy (anonymous):

cos^2=1-sin^2

Nnesha (nnesha):

right replace cos^2 x with 1-sin x^2 and then simplify

Nnesha (nnesha):

\[\frac{ \color{Red}{1 - sin^2 \theta}+\sin^2\theta-2\sin \theta + 1 }{ \cos \theta(1-\sin \theta) }\]

OpenStudy (anonymous):

\[\frac { 1-\sin \theta + \sin^2\theta - 2\sin \theta + 1 } { \cos \theta(1-\sin \theta) }\]

Nnesha (nnesha):

sin^2 ** u forgot the 2 :=)) now try to simplify that

OpenStudy (anonymous):

can the 1-sin theta cancel out?

Nnesha (nnesha):

what 1-sintheta are you talking about ? what did you get at the numerator ? :=))

OpenStudy (anonymous):

would it be this? I'm so confused... \[\frac {\sin^2\theta-2\sin \theta + 1} { \cos \theta }\]

Nnesha (nnesha):

well cos^2 theta = 1-cos^2 so substitute \[\frac{ \color{Red}{1 - sin^2 \theta}+\sin^2\theta-2\sin \theta + 1 }{ \cos \theta(1-\sin \theta) }\] now simplify the numerator first

Nnesha (nnesha):

combine like terms!!

Nnesha (nnesha):

1-sin^2x+sin^2x -2sinx +1 what are like terms ?

OpenStudy (anonymous):

sin^2x

OpenStudy (anonymous):

so it's 2-2sinx?

Nnesha (nnesha):

right !! now take out the common factor from the numerator \[\frac{ 2 - 2\sin \theta }{ \cos (1-\sin theta) }\]

OpenStudy (anonymous):

2/cos theta! or 2sec theta! (My professor wants it in terms of sec)

Nnesha (nnesha):

alright then 2 sec theta !!

OpenStudy (anonymous):

Thank you so much! :D

Nnesha (nnesha):

np , great work!!

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