Let λ and α be real. The set of all values of x for which the system of linear equations
λ x + (sin α) y + (cos α) z = 0
x + (cos α) y + (sin α) z = 0
– x + (sin α) – (cosα) z = 0 has a non-trivial solution, is
(a) [0, √2]
(b) [- √2, 0]
(c) [- √2, 2]
(d) of these
