Hi again x.x

I'm having a huge problem with these, here goes:

It is given that a=2sinθ + cosθ and b=2cosθ + sinθ where 0° ≤ θ ≤ 360°

(i) Show that a ² + b ² is constant for all values of θ

(ii) Given that 2a = 3b show that tanθ = 4/7 and find the corresponding values of θ

My answer for (i): 5sin²θ + 5cos²θ = θ by adding A and B squared.

For (ii) I don't understand the question.

Also, could someone point me to a website containing detailed explainations and examples of these? I feel like I only half understand them :/

Thanks again guys