- #1
songoku
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Homework Statement
Three units vectors a, b, and c have property that the angle between any two is a fixed angle [tex]\theta[/tex]
(i) find in terms of [tex]\theta[/tex] the length of the vector v = a + b + c
(ii) find the largest possible value of [tex]\theta[/tex]
(iii) find the cosine of the angle [tex]\beta[/tex] between a and v
Homework Equations
unit vector = vector with length 1unit
magnitude of vector = [tex]\sqrt{x^2+y^2+z^2}[/tex]
[tex]\cos \theta = \frac{r_1\cdot r_2}{|r_1||r_2|}[/tex]
The Attempt at a Solution
(i) I think I get it right. The answer is [tex]\sqrt{3+6\cos \theta}[/tex]
(ii) I don't know how to do this. I think [tex]\theta < 90^o[/tex] , but I can't find the exact value
(iii)
[tex]\cos \beta = \frac{a\cdot v}{|a||v|}[/tex]
After some calculation,
[tex]\cos \beta = \frac{2+\cos \theta}{\sqrt{3+6\cos \theta}}[/tex]
Can it be simplified further?
Thanks a lot