katrinaaap Group Title cos theta= - square root 2 divided by 2 one year ago one year ago

1. Mertsj Group Title

$\cos \theta= -\frac{\sqrt{2}}{2}$

2. katrinaaap Group Title

yeah I need to solve the equation (0<theta<2pi)

3. Mertsj Group Title

We see that the cosine is negative. In what quadrants is the cosine negative?

4. katrinaaap Group Title

2 and 3

5. Mertsj Group Title

And on your unit circle, what angle has sqrt2/2 for its cosine?

6. katrinaaap Group Title

-45

7. Mertsj Group Title

45 does have that cosine ut we said we would be in quadrants II and III where the cosine is negative. Also you said your answer had to be between 0 and 2 pi so I think you should give the answer in radians.

8. Mertsj Group Title

How many radians is 45 degrees?

9. katrinaaap Group Title

45 degrees is pi/4

10. Mertsj Group Title

So...in quadrants II and III:

11. Mertsj Group Title

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12. Mertsj Group Title

What is the angle meassured from the positive x axis?

13. katrinaaap Group Title

135

14. Mertsj Group Title

15. katrinaaap Group Title

3pi/4

16. Mertsj Group Title

Yes. And now for the third quadrant answer:

17. katrinaaap Group Title

5pi/4

18. Mertsj Group Title

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19. Mertsj Group Title

Very good. And now you have your two answers. The angles between 0 and 2 pi that have a cosine of -sqrt2/2 are 3pi/4 and 5pi/4

20. katrinaaap Group Title

perfect