- #1
Ordain
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Homework Statement
Vectors A and B have the same magnitude. Given that the magnitude of A + B is 75 times greater than the magnitude of A - B, find the angle between them?
Homework Equations
We know that A=B, so:
2AB+2ABCos[itex]\theta[/itex]=75(2AB-2ABCos[itex]\theta[/itex])
Given that A=B
2A2+2A2Cos[itex]\theta[/itex]=75(2A2-2A2Cos[itex]\theta[/itex])
3. Attempt at a solution
2A2+2A2Cos[itex]\theta[/itex]=75(2A2-2A2Cos[itex]\theta[/itex])
Couldn't get latex to work for the fraction so:
2A2+2A2Cos[itex]\theta[/itex] divided by (2A2-2A2Cos[itex]\theta[/itex])=75
Factor out 2A2:
[itex]\frac{1+Cos}{1-cos}=75
1+Cos[itex]\theta[/itex]=75-75[itex]\theta[/itex]
-74=-76Cos[itex]\theta[/itex]
Cos[itex]\theta[/itex]=74/76
[itex]\theta[/itex]=Cos-1(74/76)
[itex]\theta[/itex]=13.2 deg
Apparently this is wrong, how so?