F.4 maths.

1: slove 2sinβ+1 =0 where 0° < β < 360°

2: simplify tanβ cosβ+ 4sin(180°-β)

3: evaluate tan150°+cos330°

4: Prove the identity sin^4β-cos^4β≡ 2sin^2β-1

5: consider y= ksin(β- 20°) where 0° < β < 360° and k>0,
the naximum value of y is 4.
(a) find the value of k.
(b) find the minimum value of y and the corresponding value of β

7: in △ABC, ∠A : ∠B : ∠C =4:5:6 and AB =15cm.
Find the perimeter of △ABC.