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# Maths ALevel C3 help watch

1. Hey guys, does anyone know how to solve tan2x = -1? like how do you work out the values of x using this? Thanks!
2. (Original post by Maha1999)
Hey guys, does anyone know how to solve tan2x = -1? like how do you work out the values of x using this? Thanks!
That's C2 stuff, you have to tan^-1(-1) and double the range your given to get a set of solutions
3. (Original post by bruh2132)
That's C2 stuff, you have to tan^-1(-1) and double the range your given to get a set of solutions
Ahh okay, thanks so much!!
4. (Original post by bruh2132)
That's C2 stuff, you have to tan^-1(-1) and double the range your given to get a set of solutions
Wait but when i do tan^-1(-1), i get 2x= -1/4 pi, however the answer in the book I am using says 2x=3/4 pi ?
5. you need to use the double angle formula for tan2x
6. (Original post by heisenbatch)
you need to use the double angle formula for tan2x
Ohhh thank you soo muchh!
7. (Original post by heisenbatch)
you need to use the double angle formula for tan2x
What? That's not needed!

(Original post by Maha1999)
Wait but when i do tan^-1(-1), i get 2x= -1/4 pi, however the answer in the book I am using says 2x=3/4 pi ?
When you arctan (inverse tan) some value you will get as the principle solution (meaning the closest one to 0). Depending on your interval, there are many more solutions since tan has a period of so you'll get grab more solutions as you keep adding or subtracting from your principle solution. So generally you get where is some integer of your choice (principle solution is given when n=0)

In your case, notice how is your principle solution but , with here, hence the other solution.
8. (Original post by RDKGames)
What? That's not needed!

When you arctan (inverse tan) some value you will get as the principle solution (meaning the closest one to 0). Depending on your interval, there are many more solutions since tan has a period of so you'll get grab more solutions as you keep adding or subtracting from your principle solution. So generally you get where is some integer of your choice (principle solution is given when n=0)

In your case, notice how is your principle solution but , with here, hence the other solution.
Omg thank you so much! I was soo confused ahahah xD Anyways thank you so much for your help, much appreciated!!!

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