Finding the angle between 2 vectors problems

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SUMMARY

The discussion focuses on finding the angle of intersection between two curves represented by the helix r1(t) and the curve r2(t) at the point (1,0,0). The user encountered difficulties in calculating the dot product of the derivatives of these vectors after determining the intersection point. The correct approach involves evaluating the derivatives at the intersection point and using the known coordinates to derive the necessary values, ultimately leading to the conclusion that the angle of intersection is π/2.

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mr_coffee
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The directions say, The helix r1(t) intersects the curve r2(t) at the point (1,0,0). Find the angle of intersection of these curves. Well here is my work, and I'm stuck, how am i suppose to find the dot product of these 2 vectors once i take the derivative? the sin(1) is not a pretty number, and the book gets an asnwer of Pi/2 i think. What did i do wrong? Thanks.
Work:
http://show.imagehosting.us/show/799218/0/nouser_799/T0_-1_799218.jpg
 
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(1,0,0) refers to the (x,y,z) coordinates of the intersection point---not the value(s?) of the t-parameter at the intersection point.
From your work... [let P be the intersection]
r1(at P)=(cos t_P, sin t_P, t_P)
r2(at P)=(1+t_P,t_P^2,t_P^3)
and, P=(1,0,0).
So, from the first equation: cos t_P=1 , sin t_P=0, t_P=0,
and from the second equation: ... you can do this part
and finish off the problem.
 

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