Estimate y using differentials [Eq. (3)]. 13. y = cos x, a = /6, dx = 0.014

Estimate Δy using differentials [Eq. (3)].
13. y = cos x, a = π/6, dx = 0.014
15. y = 10 − x2/2 + x2, a = 1, dx = 0.01