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Can Vectors with an angle 180(degrees+) have a negative magnitude?

by SaltyBriefs
Tags: components, homework, signs, trigonometry, vectors
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SaltyBriefs
#1
Sep16-11, 05:05 PM
P: 10
1. The problem statement, all variables and given/known data
Can vectors with 180+(degrees) have a negative magnitude? I'm trying to find components of a vector that is going 260 km, 48 (degrees) south of east. So I'm confused whether the 260 is positive or not because of the -48 degrees.


2. Relevant equations
([itex]\vec{V}[/itex]) (sin[itex]\theta[/itex])
([itex]\vec{V}[/itex]) (cos[itex]\theta[/itex])

3. The attempt at a solution
(-260km)(sin(48)) or (260km)(sin(48)) =[itex]\vec{V}[/itex][itex]_{y}[/itex]

(-260km)(cos(48)) or (260km)(cos(48)) =[itex]\vec{V}[/itex][itex]_{x}[/itex]

Which one??
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WatermelonPig
#2
Sep16-11, 05:11 PM
P: 140
sin(x) = -sin(-x)

cos(x) = cos(-x)

Hope that helps.

Just use the convention that counterclockwise is postive and clockwise is negative in terms of measuring an angle.
SaltyBriefs
#3
Sep16-11, 05:18 PM
P: 10
Quote Quote by WatermelonPig View Post
sin(x) = -sin(-x)

cos(x) = cos(-x)

Hope that helps.

Just use the convention that counterclockwise is postive and clockwise is negative in terms of measuring an angle.
Thank you this helped so much! But um just a quick question, why is sin negative? O.o

SaltyBriefs
#4
Sep16-11, 05:20 PM
P: 10
Can Vectors with an angle 180(degrees+) have a negative magnitude?

Quote Quote by SaltyBriefs View Post
Thank you this helped so much! But um just a quick question, why is sin negative? O.o
Oh wait is this from cos, sin
and since it is in the 4th quadrant, y is negative (sin) and x is positive (cos)


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