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Mathematics 21 Online
OpenStudy (anonymous):

Simplify the trigonometric expression.

OpenStudy (anonymous):

OpenStudy (anonymous):

@kola908

OpenStudy (nincompoop):

do you have your list of trig identities?

OpenStudy (anonymous):

No idea how to do this! sorry

OpenStudy (nincompoop):

OpenStudy (nincompoop):

let me see you try to solve without thinking that sine is sine. think of it as regular x and see where that will take you

OpenStudy (nincompoop):

\[\frac{ 1 }{ 1+x }+\frac{ 1 }{ 1-x }\] can you solve this?

OpenStudy (anonymous):

I told you I have no idea how to do this.. sorry..

OpenStudy (nincompoop):

hmm can you solve this ?\[(1-x) (1+x) \]

OpenStudy (anonymous):

1x^2

OpenStudy (nincompoop):

?

OpenStudy (nincompoop):

"FOIL" method

OpenStudy (nincompoop):

\[(A+B) (A-B) = A*A -A*B +A*B+B*B \] simplifies to \[A^2+B^2\]

OpenStudy (anonymous):

ok

OpenStudy (nincompoop):

\[1+\sin^2\theta \] right?

OpenStudy (nincompoop):

are you making any connection?

OpenStudy (anonymous):

means 1

OpenStudy (nincompoop):

I think you need help way beyond trigonometry :(

OpenStudy (nincompoop):

going back to introduction to algebra

OpenStudy (mathstudent55):

@nincompoop I'm sure you meant \(\large (A + B)(A - B) = A^2 \color{red}- B^2\) and \( \large (1 + \sin \theta)(1 - \sin \theta) = 1 \color{red}- \sin^2 \theta\)

OpenStudy (nincompoop):

uyeah thanks for correcting

OpenStudy (mathstudent55):

yw

OpenStudy (anonymous):

can someone just please show me step by step please

OpenStudy (mathstudent55):

You are adding two fractions. That means you need a common denominator.

OpenStudy (mathstudent55):

The LCD is \( (1 + \sin \theta)(1 - \sin \theta) \)

OpenStudy (nincompoop):

\[1-\sin^2 \theta = \cos^2 \theta\]

OpenStudy (mathstudent55):

We need to multiply the left fraction by \( \dfrac{1 - \sin \theta}{1 - \sin \theta}\) and the right fraction by \( \dfrac{1 + \sin \theta}{1 + \sin \theta}\)

OpenStudy (nincompoop):

see \[\frac{ 1 }{ \cos \theta } = \sec \theta\] you don't have to know a lot you just need to make sure you can start deducing the possible answers

OpenStudy (nincompoop):

so this means that our answer contains \[\sec^2 \theta\]

OpenStudy (anonymous):

A... 2 Sec^3 O

OpenStudy (nincompoop):

it can't have an order magnitude of 3 because our denominator has only an order of 2

OpenStudy (anonymous):

well its the only answer with sec

OpenStudy (anonymous):

Please this is my last question...

OpenStudy (anonymous):

i meant 2 sec 2... look at A

OpenStudy (mathstudent55):

\(\dfrac{1}{1 + \sin \theta} + \dfrac{1}{1 - \sin \theta} \) \(= \dfrac{1}{1 + \sin \theta} \times \dfrac{1 - \sin \theta}{1 - \sin \theta} + \dfrac{1}{1 - \sin \theta} \times \dfrac{1 + \sin \theta}{1 + \sin \theta}\) \(= \dfrac {1 - \sin \theta} {(1 + \sin \theta)(1 - \sin \theta) } + \dfrac{1 + \sin \theta}{(1 + \sin \theta)(1 - \sin \theta)}\)

OpenStudy (anonymous):

Im choosing A

OpenStudy (nincompoop):

you are correct but you need to know the techniques

OpenStudy (mathstudent55):

\(= \dfrac {1 - \sin \theta} {1 - \sin^2 \theta } + \dfrac{1 1 + + \sin \theta}{1 - \sin^2 \theta}\) \(= \dfrac {1 - \sin \theta +1 - \sin^2 \theta }{1 - \sin^2 \theta}\) \(= \dfrac {2}{\cos^2 \theta}\) \(= 2 \sec^2 \theta\)

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