Trigonometric Equation Help (1 Viewer)

[FesuY]

Everytime a question that has the domain (-π, π) always stuffs me up. Could anyone help me out with these types of questions?

 

[Lith_30]

You could shift the domain to something that is easier for questions for example

Say for question a originally you would have to solve for but by shifting the domain by pi forward you get for which can be further modified to match what is in the cos function .

After solving the equation a little, you should arrive at

Which is in the required domain.

 

[FesuY]

You could shift the domain to something that is easier for questions for example

Say for question a originally you would have to solve for but by shifting the domain by pi forward you get for which can be further modified to match what is in the cos function .

After solving the equation a little, you should arrive at

Which is in the required domain.

Thats what I thought, however for this question the answer is 90, -150 and -30, and my answer was 90, 210, -150 and -30

 

[Lith_30]

Thats what I thought, however for this question the answer is 90, -150 and -30, and my answer was 90, 210, -150 and -30

Assuming the same domain applies as the previous equation

Thus solving for will get us



So the 210 is not included.

You could also look at the original domain and see of the answers fit within it, since 210 does not fit within the original domain you you can disregard it.