A-MTH Trigonometry (Quick)

4. consider the equation x^3 - (厂2 +1)x^2 + (厂2 -k)x +k = 0 where k is a constant.
(a) Prove that x=1 is a root of the equation. (b) Suppose sinA, sinB and sinC, where A,B,C are the angles of triangle ABC, are the roots of the equation, and A is the larest angle.
(i) Find the angles A,B,C. (ii) Find the value of k.
7. By expressing 6 sin x + 8 cos x in form r sin (x+a), find the general solution of the equation 6 sin x + 8 cos x = 5 and give your answer correct to the nearest degree.