I can't seem to do (a)(ii) of this question, there are probably two ways to do it but i get stuck using my way.

Given find the value of E and the value of where R>0 and 0<

[I got R = 5 and [tex]\alpha=0.6435 rads which is right]

Hence ind all values between 0 and 2 satisfying

(a)(i) 4cos

[i also got this right its 1.8 and 5.77 rads]

(ii) 4cos

i expanded again and got 5cos( but i dont know where to go from here,,,ive come across a similar scenario before and cant remember what I did, If anybody could help that'd be great, thnx