Hey guys, im really stuck on a question from my maths homework, mainly because in school we have never done an addition formula with more than two terms in each set of brackets, any help would be greatly appreciated.

This is what i have so far:

(cosP+cosG+cosF)*+ (sinP+sinG+sinF)*

= (cos*P+2cosPcosGcosF+cos*F) + (sin*P+2sinPsinGsinF+sin*F)

= 1+1+(2cosPcosGcosF) + (2sinPsinGsinF)

= 2+2(cosPcosGcosF+sinPsinGsinF)

= 2+2cos(P-G-F)

= 2[1+cos(P-G-F)]

PS: the * refers to a squared term, i didnt know how to type it in the forum