Sol'n: Law of Cosines - Find Direction to Return After Walking 220m, 50m

  • Thread starter panthergk
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In summary, the conversation discusses using the law of cosines and the sine rule to find the distance and direction needed to return to the starting point after walking 220.0 m due west and then turning 45.00 degrees toward north and walking another 50.00 m. The law of cosines is used to find the length of side c and the angle measure of 135 degrees, while the sine rule is used to find the direction needed to return to the starting point.
  • #1
panthergk
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Homework Statement



You walk 220.0 m due west, then turn 45.00 degrees toward north and walk another 50.00 m. how far and in what direction do you need to walk to get back to where you started?

Homework Equations


Law of Cosines


The Attempt at a Solution



I did the law of cosines to find the lenngth of side c. I used the angle measure of 135 degrees. I am not sure how to find the direction though. What degree is it?
 
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  • #2
Welcome to PF!

panthergk said:
I did the law of cosines to find the lenngth of side c. I used the angle measure of 135 degrees. I am not sure how to find the direction though. What degree is it?

Hi panthergk! Welcome to PF! :smile:

YOu now have one angle and all three sides, and you want another angle …

so use the sine rule. :wink:
 
  • #3




Great job using the Law of Cosines to find the length of side c! To find the direction you need to walk to return to your starting point, you can use the Law of Sines. Since you know the lengths of two sides and the angle between them, you can use the formula sin(A)/a = sin(B)/b = sin(C)/c to find the sine of the angle opposite to the side you are looking for. Then, you can use inverse sine function to find the measure of this angle. This will give you the direction you need to walk in to return to your starting point. Remember to take into account the directions you have already walked in (west and north) to determine the final direction. Good luck!
 

Related to Sol'n: Law of Cosines - Find Direction to Return After Walking 220m, 50m

1. How is the Law of Cosines used to find direction in this problem?

The Law of Cosines is used to find direction in this problem by calculating the angle between the initial and final positions of the walker. By using the formula c² = a² + b² - 2abcosC, where c is the distance between the two positions, a and b are the lengths of the sides adjacent to the angle C, and C is the desired direction, the angle C can be solved for and used as the direction to return.

2. Can the Law of Cosines be used to find direction in any situation?

No, the Law of Cosines can only be used to find direction when the triangle formed by the initial and final positions and the desired direction is a non-right triangle. If the triangle is a right triangle, the Law of Cosines cannot be used and the Law of Sines or basic trigonometry must be used instead.

3. What is the difference between the Law of Cosines and the Law of Sines?

The Law of Cosines and the Law of Sines are both used to solve triangles, but the main difference is the type of triangle they can be used for. The Law of Cosines can only be used for non-right triangles, while the Law of Sines can be used for any type of triangle. The Law of Cosines also involves finding a missing side or angle, while the Law of Sines involves finding ratios of sides and angles.

4. How can the Law of Cosines be applied in real-life situations?

The Law of Cosines can be applied in various real-life situations, such as navigation and surveying. It can be used to find distances and angles between two points, which is useful in determining direction and location. It can also be used in physics and engineering to solve for forces and velocities in non-right triangle situations.

5. Is the Law of Cosines always accurate?

Like any mathematical formula, the Law of Cosines is only accurate if the given information and calculations are correct. If there are measurement errors or incorrect inputs, the result may not be accurate. It is important to double-check all given values and calculations before using the Law of Cosines to ensure accuracy.

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