Question

Вычислите | а + b | и | а - b |, если | а | = 5, | b | = 8, аb = 60°.

Answer 1

| а + b |=корень(a^2+b^2-2a*b*cos(pi-ab)) =корень(5^2+8^2-2*5*8*cos(pi-pi/3)) = корень(129) ~ 11,35782
| а - b |=корень(a^2+b^2+2a*b*cos(pi-ab)) =корень(5^2+8^2+2*5*8*cos(pi-pi/3)) = 7