- #1

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Sin2x-1=0

I thought I recognized that Sin2x is from the double angle identities chapter so I substituted [2CosSin] for Sin2x.

So I ended up with 2CosSin=1 ( I moved the one over)

...and then I got stuck... am I attacking this wrong? :grumpy:

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- Thread starter Determined77
- Start date

In summary, the person is trying to solve trig identities but gets stuck. They substitute [2CosSin] for Sin2x and get 2CosSin=1. They then get stuck and ask for help.f

- #1

- 2

- 0

Sin2x-1=0

I thought I recognized that Sin2x is from the double angle identities chapter so I substituted [2CosSin] for Sin2x.

So I ended up with 2CosSin=1 ( I moved the one over)

...and then I got stuck... am I attacking this wrong? :grumpy:

- #2

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- #3

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If I took sin-1 from both sides would I get 2x=1 and

Sin-1(1) or 90 degrees?

- #4

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Anyway, I meant do this: sin

As you rightly said, sin

What does the left hand side, sin

- #5

Homework Helper

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[tex]\sin(2x)=1[/tex]

[tex]\arcsin(\sin(2x)) = \arcsin 1[/tex]

[tex]2x= \arcsin (1)[/tex]

[tex]x = \frac{\arcsin 1}{2}[/tex]

- #6

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arcsin(sin(2x))= arcsin(1) ==> 2x= arcsin(1)

(Other notation for the same thing:sin

Now that you have 2x= arcsin(1) you get rid of the "2" by again "doing the opposite"- the opposite of multiplying by 2 is dividing by 2:

2x/x= x= arcsin(1)/2 or x= sin

If you want a specific decimal approximation to that answer, your calculator should have a "sin

- #7

Homework Helper

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Note arcsin 1 = [tex]\pi/2 + 2k\pi , k \in \mathbb{Z}[/tex]

- #8

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Note arcsin 1 = [tex]\pi/2 + 2k\pi , k \in \mathbb{Z}[/tex]

Well, if you want to do the

- #9

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Its much easier to get the values if the problem stays in one trig func.I thought I recognized that Sin2x is from the double angle identities chapter so I substituted [2CosSin] for Sin2x.

So I ended up with 2CosSin=1 ( I moved the one over)

...and then I got stuck... am I attacking this wrong? :grumpy:

- #10

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Its much easier to get the values if the problem stays in one trig func.

Did you not read every other reply in this thread?...

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