Bonjour,
x = cos(t)
y = 2cos(t) - cos(2t)
Q1)
cos(2t) = 2cos²(t) - 1
⇒ y = 2x - 2x² - 1
⇒ trajectoire parabolique
Q2)
vx(t) = dx/dt = -sin(t)
vy(t) = dy/dt = -2sin(t) + 2sin(2t)
ax(t) = dvx/dt = -cos(t)
ay(t) = dvy/dt = -2cos(t) + 4cos(2t)
A t = π/3 :
vx(π/3) = -√3/2 et vy(t) = -√3 + √3 = 0
⇒ ||v|| = √3/2
ax(π/3) = -1/2 et ay(t) = -1 - 2 = -3
⇒ ||a|| = √[3/4 + 9] = √(39/4)
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Bonjour,
x = cos(t)
y = 2cos(t) - cos(2t)
Q1)
cos(2t) = 2cos²(t) - 1
⇒ y = 2x - 2x² - 1
⇒ trajectoire parabolique
Q2)
vx(t) = dx/dt = -sin(t)
vy(t) = dy/dt = -2sin(t) + 2sin(2t)
ax(t) = dvx/dt = -cos(t)
ay(t) = dvy/dt = -2cos(t) + 4cos(2t)
A t = π/3 :
vx(π/3) = -√3/2 et vy(t) = -√3 + √3 = 0
⇒ ||v|| = √3/2
ax(π/3) = -1/2 et ay(t) = -1 - 2 = -3
⇒ ||a|| = √[3/4 + 9] = √(39/4)