## amhishaw 2 years ago 2 cos theta = 1, find all solutions

1. Brittni0605

Step by step help?

2. amhishaw

yes

3. Brittni0605

Ok, so think of theta as a variable

4. Brittni0605

if theta was an 'x' how would you solve?

5. amhishaw

to be honest I have no clue.

6. shaik0124

2 cos theta=1 cos theta=1/2 theta=cos inverse(1/2) theta=60degrees

7. amhishaw

ok, so i would divide 2 from both sides?

8. Brittni0605

Yes.

9. Brittni0605

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10. Brittni0605

Now, you know cos theta equals 1/2..now you want to find theta, do you know how?

11. amhishaw

oh! okay and would I just look for cos (x) value on the unit circle right?

12. Brittni0605

Umm, you could do that. But im not sure if you would have the unit circle with you on your tests.

13. Brittni0605

There is another way to do it, if you have a graphing calc or if you memorized the cos and sin values of the major degrees on the circle.

14. amhishaw

well no lol my precal teacher was trying to explain how to but I couldn't understand

15. amhishaw

without it*

16. Brittni0605

Ohh, ok. Well try to memorize the major degrees..like 30, 60, 45, 90, 180, 270, 360.

17. Brittni0605

But if you were to use your unit circle, you would look for the degrees with a cos (x value) of 1/2

18. Brittni0605

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19. amhishaw

ok, so would i use ALL of the radian values of cos 1/2?

20. Brittni0605

do you know the cos and sin values of the angles I drew?

21. Brittni0605

Yes, all of the values, bc the problem says find ALL

22. amhishaw

I know most of them

23. amhishaw

thank you so much, you've been a lot of help

24. amhishaw

so the solutions would be pi/3 and 5pi/3?

25. Brittni0605

Yes.

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