STEP II 1995 question 6 solution

TSR Wiki]] > Study Help > Exams and Qualifications > A Levels > STEP > STEP II 1995 question 6 solution

.

.

The other 7th roots of unity are the roots of the equation:

.

.

Hence:

.

Hence:

.

Hence:

.

Consider:

.

Hence:

.

.

The function of "x", is increasing from to . It is positive from to , and negative from to (the behaviour after is not relevant to this question).

.

Hence one wishes to have the positive value for the aforementioned "imaginary part":

.