Hey Guys, could you help me out here please?

i am having difficulties figuring out this question on my assignment

Express f(theta)=3 cos(theta) - 4 sin(theta) in the form rcos(theta)+1

0<=r and 0<=(alpha)<=pi/2

and find the (i)Find the Maximum value of f(theta)

(ii)Find the minimum value of 1/8+f(theta)

and NO.2- Given that sum of angles ABC of a triangle is pi radians, show that sinA =sin(b+c)

part b : sinA+sinb+sinc=sin(a+b)+ sin(b+c)+sin(a+c)

i am having difficulties anwsering these two questions as i have not yet to learn them in class yet....the teacher has not taught us this yet but still gave it to us :(

{caribbean teachers at my school}

would really appreciate a work through with this one, as no body in my class knows how to do it^

Thank you very much

Re: Hey Guys, could you help me out here please?

Hey adrenaline1996.

A hint for 2 is that in a triangle, A = pi - B - C since A + B + C = pi. So you have to show that sin(A) = sin(pi - B - C) = sin(B + C).

(Take into account that sin(-x) = -sin(x) and sin(x + pi) = -sin(x)).

In terms of minimum and maximum values, you should look at the first and second derivatives. Have you covered derivatives in class?