Distance of lake a is 200 km at 20 degree north of east
distance between lake a and b is 230 km at 30 degree west of north
now the distance between base and lake b is given as
[tex]d = d_1 + d_2[/tex]
given that
[tex]d_1 = 200 cos20 i + 200 sin20 j[/tex]
[tex]d_1 = 187.94 i + 68.4 j[/tex]
[tex]d_2 = -230 sin30 i + 230 cos30 j[/tex]
[tex]d_2 = -115 i + 199.2 j[/tex]
now the total distance is
[tex]d = (187.94 - 115)i + (199.2 + 68.4)j [/tex]
[tex]d = 72.94 i + 267.6 j[/tex]
now the magnitude of the distance is given as
[tex]d = \sqrt{72.94^2 + 267.6^2}[/tex]
[tex]d = 277.4 [/tex]
also the direction is given as
[tex]\theta = tan^{-1}\frac{267.6}{72.94}[/tex]
[tex]\theta = 74.7 degree[/tex]
so it is 277.4 km at 74.7 degree North of East