Consider the helix represented by the vector-valued function \r(t)

Carolyn Moore

Carolyn Moore

Answered question

2021-12-03

Consider the helix represented by the vector-valued function r(t)=2cost,2sint,t.
(a) Write the length of the arc s on the helix as a function of t by evaluating the integral
(b) Solve for tin the relationship derived in part (a),and substitute the result into the original vector-valued function.This yields a parametrization of the curve interms of the arc length parameter s.
(c) Find the coordinates of the point on the helix for arc lengths s=5 and s=4.
(d) Verify that r(s)=1.
s=0t[x(u)]2+[y(u)]2+[z(u)]2du.

Answer & Explanation

Anthony Caraballo

Anthony Caraballo

Beginner2021-12-04Added 15 answers

Step 1
We have given that;
A helix represented by the vector-valued function r(t)=(2cost,2sint,t)
Step 2
(a) From the given position vector, we have parametric equations;
x(t)=2cos
y(t)=2sin
z(t)=t
we differentiate these equations and get;
x(t)=2sin
y(t)=2cos
z(t)=1
We have given integrel;
=0tx(u)2+y(u)2+z(u)2du.
=0t(2sinu)2+(2cosu)2+12du.
=0t4sin2u+4cos2u+1du
=0t4+1du
=0t5du
=5t
Step 3
(b) From the part (a) we have;
s=5t
t=s5
On plugging this value in the parametric equations,we get;
x(s5)=2coss5
y(s5)=2sins5
z(s5)=s5
So the function of given curve in the form of s will be;
r(s)=2coss5,2sins5,s5
Step 4
{c) We have given the curve;
r(s)=2coss5,2sins5,s5
On plugging s=5 in the equation, we get;
r(5)=2cos55,2sin55,55

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