Problema Solution
Anya walks 2km due north, then turns and walks another 3kmin the direction N 35degrees W. Find her distance and bearing from her starting point.
Answer provided by our tutors
Sketch the movement.
The angle formed by the 2km and 3km legs is the supplement of the 35 degree angle west of north:
180 - 35 = 145 degrees
We now know the length of two sides and one angle.
The side opposite the known angle is the direct distance, 'a', (a >=0) between the starting and ending points.
Using the Law of Cosines:
a^2 = b^2 + c^2 - 2bc(cosA)
a^2 = 2^2 + 3^2 - 2*2*3*(cos(145))
by solving we find:
a = 4.78km (positive root)
click here to see the step by step calculation:
To determine the bearing from the starting point, we must determine the angle, C, between the first leg and the direct path.
Using the Law of Sines:
4.78/sin145 = 3/sinC
by solving we find:
C = 21.1 degrees
So the distance and bearing of the endpoint from the starting point is 4.78km North 21.1 degrees West.