Problem involving cos + sin: express 5cos(3t) + 12sin(3t) as "A cos(wt + a)"
\mbox{Express }\, 5\, \cos(3t)\, +\, 12\, \sin(3t),\, \mbox{ in the form}
A\, \cos(\omega t\, +\, \alpha),\, \alpha\, \geq\, 0\, \mbox{ and can be written}
\mbox{as degrees or radians.}
If any help as to how to...