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# Finding the values of trig equations watch

1. I am using the school's MyMaths login right now, and I'm revising trig equations, but I can't figure out the reason for one of the answers.

I understand that most of the incorrect answers were rounding errors, but for sin 3θ = -1, I don't understand how to get 1.57 as an answer. I figured out that I can get 3.67 and 5.76 by doing π - (-1/6(π)) and 2π + (-1/6(π)), but I don't understand how to find 1.57.

How do I find out all the values of θ for sin 3θ = -1?
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2. (Original post by ashjack)
I am using the school's MyMaths login right now, and I'm revising trig equations, but I can't figure out the reason for one of the answers.
I understand that most of the incorrect answers were rounding errors, but for sin 3θ = -1, I don't understand how to get 1.57 as an answer. I figured out that I can get 3.67 and 5.76 by doing π - (-1/6(π)) and 2π + (-1/6(π)), but I don't understand how to find 1.57.

How do I find out all the values of θ for sin 3θ = -1?
. And of course another solution is given by

So

Then add on to both solutions to get again, and you also have

Then add on again to both solutions and the latter should give you your 5.76.
3. (Original post by RDKGames)
. And of course another solution is given by

So

Then add on to both solutions to get again, and you also have

Then add on again to both solutions and the latter should give you your 5.76.
Thank you for your reply, I think I understand now. Just to clarify, you used the value of in the original trig equation to find 1.57?
4. (Original post by ashjack)
Thank you for your reply, I think I understand now. Just to clarify, you used the value of in the original trig equation to find 1.57?
What do you mean I used ?? I can't really use it when I'm trying to find it.

I used the fact that solutions to are given by and from small integers (in this case )

If you let then you have and

Then you can solve for in your wanted range.
5. (Original post by RDKGames)
What do you mean I used ?? I can't really use it when I'm trying to find it.

I used the fact that solutions to are given by and from small integers (in this case )

If you let then you have and

Then you can solve for in your wanted range.
Thank you, I do understand now. I just need to work on knowing which number to add to and which to take away from when using a Sine graph

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