AIBU to ask a Maths question?

[Orchid6578]

DD is revising for Further Maths A-Level. She is trying to answer questions 4a and 4b. See pictures attached.

She has found all the correct roots but is confused by the fact that there are so few roots included in the diagram on the Marks scheme.

Is the Marks scheme wrong or has she missed a trick?

You need to ask @noblegiraffe for some help.

Bit too blurry to read, but is it that she should only be finding answers for the range +/- pi, and she’s found more answers for outside that range?