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Mathematics 18 Online
OpenStudy (airyana1114):

I need help with Pythagorean identity.

OpenStudy (airyana1114):

if sin(x) = 1/2, what is cos(x) and tan(x)?

OpenStudy (photon336):

\[\sin(x) = \frac{ 1 }{ 2 }\] on a calculator you can enter in inverse sine \[sine^{-}(\frac{ 1 }{ 2 }) = x | ArcSin(\frac{ 1 }{ 2 }) = x \]

OpenStudy (photon336):

this will give you the value of the angle theta that when you take sine of that same angle you get 1/2

OpenStudy (airyana1114):

okay...you lost me at "on a calculator"

OpenStudy (airyana1114):

i need to know how to do the steps one by one

OpenStudy (airyana1114):

does cos = √ 3/4

OpenStudy (photon336):

another way would be this

OpenStudy (airyana1114):

and then tan = sin/cos

OpenStudy (photon336):

\[\sin^{2}(x)+\cos^{2}(x) = 1 \]

OpenStudy (airyana1114):

okay so i plugged in 1/2 but then i don't know my next step

OpenStudy (photon336):

So take a look at the steps below We use this identity \[\sin^{2} + \cos^{2} = 1\] \[(1/2)^{2}+\cos^{2}(x) = 1\] \[Cos^{2}x = 1-(\frac{ 1 }{ 4 })\] \[\cos^{}(x) = \sqrt{\frac{ 3 }{ 4 }}\]

OpenStudy (photon336):

so tangent x would be \[\tan(x) = \frac{ \sin(x) }{ \cos(x) }\]

OpenStudy (airyana1114):

okay so 1/2 over √ 3/4?

OpenStudy (photon336):

yep let's simplify that

OpenStudy (airyana1114):

how?

OpenStudy (photon336):

\[Tangent(x) = \frac{ 1 }{ 2*\sqrt{\frac{ 3 }{ 4 } } } = \frac{ 1 }{ 2*\frac{ \sqrt{3} }{ \sqrt{4} } } = \frac{ 1 }{ \cancel\2*\frac{ \sqrt{3} }{ \cancel\2 } } = \frac{ 1 }{ \sqrt{3} }\]

OpenStudy (airyana1114):

where is the 2 from on the denominator? is it the two from 1/2?

OpenStudy (photon336):

it's just re-written

OpenStudy (airyana1114):

okay, thank you!

OpenStudy (photon336):

we had \[\frac{ \frac{ 1 }{ 2 } }{ \sqrt{\frac{ 3 }{ 4 }} } = \frac{ 1 }{ 2*\sqrt{\frac{3 }{ 4 } }}\]

OpenStudy (airyana1114):

ohhh, okay can you help me another one?

OpenStudy (airyana1114):

@Photon336

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