1. A) Is there a number x ∈ R, so cos x = 0.8 and sin x = 0.2? b) Same question for cos x = 0.8 and sin x = 0.6 2. Show that for any x ∈ R: a) sin^{3}x + cos^{3} = (sin x + cos x)(1- sin x * cos x) b) sin^{4} x + cos^{4} x = 1 - 2sin^{2} x * cos^{2}x