Let A and B denote the statements
A : cosα + cosβ + cosγ = 0
B : sinα + sinβ + sinγ = 0
If cos(β – γ) + cos(γ – α) + cos(α – β) = − 3/2, then
(a) A is false and B is true
(b) both A and B are true
(c) both A and B are false
(d) A is true and B is false