We want to measure the distance a between two points B and C. A simple sextant is used that can measure angle 60^? very exactly. At some point A the angle between AB and AC is 60^?. It was measured that distance AB = c = 300 5m and AC = b = 800 10m. From cosine equation a² = b² + c² - 2bcos? it follows that BC = a ? 700 m.

With help of linear approximation calculate the approximative upper limit for the inaccuracy of a caused by inaccuracies of b and c.