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## Homework Statement

Vector C has a magnitude of 5.0 units and makes an angle of -90.0º with the positive x-axis, vector D has a magnitude of 7.0 units and makes and angle of –120º with the positive x-axis. What is the magnitude of the vector sum of

*C + D*? - I am assuming that this means the resultant.

## Homework Equations

General for finding the components:

[tex] A_x = Acos\theta [/tex]

[tex] A_y = Asin\theta [/tex]

Magnitude:

[tex] A = \sqrt {{A_x}^2 + {A_y}^2} [/tex]

## The Attempt at a Solution

I first start with [tex] \vec C [/tex]

[tex] C_x = 5.0 cos (-90) = 0 [/tex]

[tex] C_y = 5.0 sin (-90) = -5 [/tex]

Move on to [tex] \vec D [/tex]

[tex] D_x = 7.0 cos (-120) = -3.5 [/tex]

[tex] D_y = 7.0 sin (-120) = -6.1 [/tex]

I have all the components now, moving on to finding the

*A + B*- which I am assuming means the resultant.

[tex] R_x = 0 + (-3.5) = -3.5 [/tex]

[tex] R_y = -5 + (-6.1) = -11.1 [/tex]

[tex] R = \sqrt { (-3.5)^2 + (-11.1)^2} = 11.6 [/tex] - This is my answer to the question

Now, I am not sure if my assumption that A+B = Resultant is true. Any ideas on where I am messing up. Thank you

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