chill you dont have to ask 20 tiems
for question 7 i dont really get the visualisation method but i just halved it and then split it into parts of (sinx+cosx)/(sinx+cosx) + (cosx-sinx)/(sinx+cosx) - if u look at the possible answers they sorta made it obvious
14bii i got wrong lol but if u look at the solution it should make sense
15bii has already been explained but the way i did it was through the fact that it can't have more than 4 unique roots (and if u apply the previous part to all other solutions which must be possible, u end up with 8) and hence found the conditions such that there were only 4 unique roots (so roots are equal to each other).
16c they did it a weird way but the way I did it was just to left c= (x,y) where OA is the x direction (this is just for simplicities sake, hypothetically OA could be rotated or whatever but it would still be the same relatively to the C so the proof stands). If u think about it logically, AB must hence be (-x,y), because the lines CB and OA are parallel so the y distance is the same, and they are the same length. So then express AC and OB in terms of these new values, and THen just find the modulus or magnitude whatever its called for vectors for AC and OB and youll see theyre equal
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