Find all solutions for unkown angle.

[Zanfib]

Question is: Find all solutions for theta (to the nearest degree) if cos of theta = -0.7771

The unknown angle must be between 0 and 360 degrees.

That is all the information I have. I have no idea where to start or even what 'solutions' means in this context.

Please help.

 

[srmichael]

Question is: Find all solutions for theta (to the nearest degree) if cos of theta = -0.7771

The unknown angle must be between 0 and 360 degrees.

That is all the information I have. I have no idea where to start or even what 'solutions' means in this context.

Please help.

"Solutions" means all the angles between 0° and 360° whose cosine of that angle is -0.7771.

Have you learned about finding an angle using the inverse trig function?

 

[Zanfib]

"Solutions" means all the angles between 0° and 360° whose cosine of that angle is -0.7771.

Have you learned about finding an angle using the inverse trig function?

Sort of.

cos^-1(-0.7771) = 140.9958157 on my calculator. Is that what you mean?

However the term solutions implies that there is more than one. How should I go about finding the others?

EDIT: Found answer. 141 degrees and 219 degrees.