Submitted by Grainne on Mon, 10/02/2017 - 00:29
Forums:
In question 2ii the hints and partial solutions say you should end up with 0=2s^3-2s^2-s+1 however I don't understand why it's +1 since 2cos2A=2(1-2sin^2A)=2-4sin^2A and so I'm confused about why it's +1 rather than +2. Thanks for the help.
2ii
We have:
sin3A−sinA=2cos2A3sinA−4sin3A−sinA=2(1−2sin2A)2sinA−4sin3A=2−4sin2AsinA−2sin3A=1−2sin2A
Basically, it is "+1" as you can divide throughout by 2.