Find ∫C (x^2-5y)i + (2y^3)j dr where C consists of the three line segments from (5,0,0) to (5,1,0) to (0,1,0) to (0,1,2).
Do this one segment at a time.
(i) From (5, 0, 0) to (5, 1, 0) via r(t) = <5, t, 0> with t in [0, 1].
∫c₁ [(x^2 - 5y) dx + 2y^3 dy]
= ∫(t = 0 to 1) [(5^2 - 5t) * 0 + 2t^3 * 1] dt
= ∫(t = 0 to 1) 2t^3 dt
= 1/2.
(ii) From (5, 1, 0) to (0, 1, 0) via r(t) = <5t, 1, 0> with t in [0, 1] and opposite orientation.
∫c₂ [(x^2 - 5y) dx + 2y^3 dy]
= -∫(t = 0 to 1) [((5t)^2 - 5) * 5 + 2 * 0] dt
= -∫(t = 0 to 1) (125t^2 - 25) dt
= -(125t^3/3 - 25t) {for t = 0 to 1}
= -50/3.
(iii) From (0, 1, 0) to (0, 1, 2) via r(t) = <0, 1, 2t> with t in [0, 1].
∫c₃ [(x^2 - 5y) dx + 2y^3 dy]
= ∫(t = 0 to 1) [(0^2 - 5) * 0 + 2 * 0] dt
= 0.
So, (i)-(iii) yields ∫c [(x^2 - 5y) dx + 2y^3 dy] = 1/2 - 50/3 + 0 = -97/6.
I hope this helps!
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Verified answer
Do this one segment at a time.
(i) From (5, 0, 0) to (5, 1, 0) via r(t) = <5, t, 0> with t in [0, 1].
∫c₁ [(x^2 - 5y) dx + 2y^3 dy]
= ∫(t = 0 to 1) [(5^2 - 5t) * 0 + 2t^3 * 1] dt
= ∫(t = 0 to 1) 2t^3 dt
= 1/2.
(ii) From (5, 1, 0) to (0, 1, 0) via r(t) = <5t, 1, 0> with t in [0, 1] and opposite orientation.
∫c₂ [(x^2 - 5y) dx + 2y^3 dy]
= -∫(t = 0 to 1) [((5t)^2 - 5) * 5 + 2 * 0] dt
= -∫(t = 0 to 1) (125t^2 - 25) dt
= -(125t^3/3 - 25t) {for t = 0 to 1}
= -50/3.
(iii) From (0, 1, 0) to (0, 1, 2) via r(t) = <0, 1, 2t> with t in [0, 1].
∫c₃ [(x^2 - 5y) dx + 2y^3 dy]
= ∫(t = 0 to 1) [(0^2 - 5) * 0 + 2 * 0] dt
= 0.
So, (i)-(iii) yields ∫c [(x^2 - 5y) dx + 2y^3 dy] = 1/2 - 50/3 + 0 = -97/6.
I hope this helps!