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# Trigonometry watch

1. from the equation tan22X=3/2 how do I find tanX
Thanks
2. (Original post by daviem)
from the equation tan22X=3/2 how do I find tanX
Thanks
You have to use the double angle identity for tan(2x)
3. (Original post by lizard54142)
You have to use the double angle identity for tan(2x)
sorry, I don't understand
4. (Original post by lizard54142)
You have to use the double angle identity for tan(2x)
could you explain further?
5. square root both sides

use the identity for tan2x

http://www.uhigh.ilstu.edu/math/sond...s%20pt%202.htm
6. (Original post by daviem)
sorry, I don't understand
The identity is:

In your case, A = B
7. (Original post by lizard54142)
The identity is:

In your case, A = B
ok, thanks
8. (Original post by daviem)
ok, thanks
Do you see how to start now? The first thing to do would be get rid of the tan^2(2x) by square rooting, this will make things much easier
9. In all honesty I'm trying to a trig equation question (question 7b, aqa, pure core 2, 2014) and I'm just perplexed as to how to get the values of X.
10. (Original post by the bear)
square root both sides

use the identity for tan2x

http://www.uhigh.ilstu.edu/math/sond...s%20pt%202.htm
Thanks for that link
11. (Original post by daviem)
In all honesty I'm trying to a trig equation question (question 7b, aqa, pure core 2, 2014) and I'm just perplexed as to how to get the values of X.
Is this a different question? If so, can you post a screenshot?
12. (Original post by lizard54142)
Is this a different question? If so, can you post a screenshot?
Yeah hang on, I'll try
13. Here, the answer and the question
Attached Files
14. SR Trig exam question.docx (234.6 KB, 57 views)
15. SR Trig exam answer.docx (256.5 KB, 50 views)
16. square root then find the solutions using your preferred method such as the graph but remember to double your range as its tan2x. e.g if it was 0<x<360 make it 0<2x<720 then find values of x by halfing all the angles in the range. note if you divide by two first then find angles between 0 and 360 then you will lose solutions.
17. (Original post by Nels98)
square root then find the solutions using your preferred method such as the graph but remember to double your range as its tan2x. e.g if it was 0<x<360 make it 0<2x<720 then find values of x by halfing all the angles in the range. note if you divide by two first then find angles between 0 and 360 then you will lose solutions.
This is the correct method, for C2 anyway.

But don't forget, x is going to be - root(3/2) as well as +
18. for 7a you need to use the identity sin^2x+cos^2x=1
19. (Original post by Bobjim12)
This is the correct method, for C2 anyway.

But don't forget, x is going to be - root(3/2) as well as +
I'm only in L6 but i hear it gets a bit more complex next year
20. (Original post by Nels98)
I'm only in L6 but i hear it gets a bit more complex next year
Yeah, like a previous poster put for some double angle identity, saw similar things in AQA's formula book, probably c3/c4 stuff.
21. (Original post by daviem)
Here, the answer and the question
Oh, well you don't need to find tan(x) as you originally thought in your original post! You just have to square root, and then use inverse tan. Notice though in part b) it is in terms of , but part 1 was just in terms of
22. (Original post by Nels98)
square root then find the solutions using your preferred method such as the graph but remember to double your range as its tan2x. e.g if it was 0<x<360 make it 0<2x<720 then find values of x by halfing all the angles in the range. note if you divide by two first then find angles between 0 and 360 then you will lose solutions.
I did that, but I wasn't getting the right answers, I got my primary value as 0.886

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