Hello laurettarosa! Are you familiar with the C.A.S.T Rule? Basically, it helps us determine where the trig ratios: sin, cos, and tan are positive or negative.

Let Q = theta.

TheCinCAST is located in the4thquadrant, and onlyCosine is positive there.

TheAin CAST is located in the1stquadrant andSine,Cosine, andTan are positive there.

TheSin CAST is located in the2ndquadrant and onlySine is positive there

TheTis CASTis located in the3rdquadrant and onlyTan is positive there.

Moving on,

cos(180 - Q) : Analysing the angle: 180 - Q, this means that Q is located in the 2nd quadrant and according to CAST, only sine is positive there.

Therefore, cos(180 - Q) = - cos Q

Can you handle the rest? if you have any other questions, please do not hesitate to ask.