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July 23, 2014

July 23, 2014

Posted by **Joe** on Sunday, July 24, 2011 at 8:06pm.

Given the magnitudes of vectors u and v and the angle Ό between them, find the magnitude of the sum u + v to the

nearest tenth and the angle that the sum vector makes with u to the nearest degree.

/u/= 20, /v/= 86, Ό = 90°

The answer is 88.3 and 77deg but I don't know how to get to this. Thanks in advance

- Pre Cal/Vectors -
**Reiny**, Sunday, July 24, 2011 at 9:12pmFollow the same method and steps as I showed you in

http://www.jiskha.com/display.cgi?id=1311551145

except this one is easier since it forms a right-angled triangle, and your parallogram is a rectangle.

If the resultant is R, then

R^2 = 20^2 + 86^2

= 7796

R = √7796 = 88.29

Now use the Sine Law again to get the angle between vectors

- Pre Cal/Vectors -
**Henry**, Monday, July 25, 2011 at 5:34pmX = 20.

Y = 86.

tanA = Y/X = 86/20 = 4.3,

A = 76.9 deg.

R = X / cosA = 20 / cos76.9 = 88.24

OR

R = Y / sinA = 86 / sin76.9 = 88.3

.

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