# CALCULUS

posted by .

How do I do this: add the following vectors , 7m/s [N30E] and 2m/s [S17E] I know that you must use trigonometry and break stuff up into components and use sine and cosine law; just not sure how. Thanks!

• CALCULUS -

Do you just find the resultant?

• CALCULUS -

• CALCULUS -

Yes, you find the resultant.

Letting north be the +y axis and east be the +x axis, the components of 7 m/s [N30E] are 7 sin 30 = 3.5 along the +x axis and 7 cos 30 = 6.062 along the +y axis. Calculate the components of the other vector similarly, and add the x and y components separately for the resultant.

• CALCULUS -

I need to use trigonometry to do this though, not component law, is there any real difference?

• CALCULUS -

If you want the magnitude of the resultant, use the law of cosines. Drawing a figure will help.

The law of sines can get you the sine of any angle of the triangle formed by the two velocity vectors and the resultant.

it's easier using components, but the answer will be the same.

• CALCULUS -

Yes, ok I have done that, I drew a diagram, but the thing is, you have all these angles, the co interior angles, and I am unsure of which ones to use - you have the 30 from the NE and then there is 17 from SE but there is another one, and I am not sure how to find it. I know the equation would be R^2= (7)^2 (2)^2-2(7)(2)COS___ I am unsure about what the angle is. Thanks, sorry for being so confusing.

• CALCULUS -

I could write down a bunch of equations but since I cannot draw the triangle for you with the tools we have, it would probably be difficult to explain in words what is going on.

Draw the two velocity vectors end to end. Then close the triangle to get the resultant. The angle between the two vectors that you were provided is 47 degrees. That is the angle that you use in the law of cosines to get the magnitude of the resultant

R^2 = 7^2 + 2^2 - 2*14 cos 47 = 33.90
R = 5.82 m/s
Now use the law of sines to get the other two angles of the triangle, which will tell you the direction of the resultant.

It is a lot easier adding components.

• CALCULUS -

Thanks! I agree about the components but the question said specifically to use cosine and sine law :(. Thanks very much though!

• CALCULUS -

I used the sine law to get 15 degrees. I am unsure as to what I now do with this angle. Do I add or subtract it somewhere to find the overall angle I am looking for? Thanks again! I owe you!

## Similar Questions

1. ### Urgent SUMMER SCHOOL CALCULUS

Add these two vectors: I used component law, and I got an answer, but I am unsure as to how to do the direction at the end. Add: 9m/s [N30E] and 2m/s [N60E] I wound up with 10.8m/s and I found an angle of 55 but I am unsure as to what …
2. ### Summer School Calculus

Another one for you :P, add these two vectors using trigonometry (again)... 9N[S2W] and 11N[N31W]...Again, I am confused about the angles, I am not sure what value I should use for the cosine and sine law. THANKS AGAIN!!
3. ### Summer School Calculus

Add these two vectors: I used component law, and I got an answer, but I am unsure as to how to do the direction at the end. Add: 9m/s [N30E] and 2m/s [N60E] I wound up with 10.8m/s and I found an angle of 55 but I am unsure as to what …
4. ### Calc

Question: Using trigonometry, add these two vectors. 7m/s [N30E] and 2m/s [S17E]. THIS is my answer: 6m/s [N45E] is this the correct answer?
5. ### Summer School Calculus

Add the following vectors , 7m/s [N30E] and 2m/s [S17E], using trigonometry. Once you draw these out into diagrams, you use the triangle law yes?
6. ### Trigonometry

I had to find the sine, cosine and tangent of -150 degrees. I got - sq. root of 3/2, -1/2, and - sq. root of 3/3. But my book has -1/2 as the sine, and -sq. root of 3/3 as the cosine. Why is this?
7. ### trigonometry

Use logarithms and the law of tangents to solve the triangle ABC, given that a=21.46 ft, b=46.28 ft, and C=32°28'30" I have to use logarithms and law of tangents . and then provide the check. which says law of sine or mollweids equation. …
8. ### Physics

A horse runs 15 m [N 23° E] and then 32 m [S 35° E]. What is the total displacement of the horse?
9. ### Geometry

The word cosine literally means "the complement of the sine." Write a paragraph explaining how complements of sine and cosine are connected. I know that the sine and the cosine of complementary angles are the same. but how can i add …