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What are the critical points for the plane curve defined by the equations x(t)=4sin(2t),y(t)=-t, and 0 <= t < 2pi ? Write your answer as a list of values of t, separated by commas. For example, if you found 
t=1 or t=2, you would enter 1,2 .

What are the critical points for the plane curve defined by the equations x(t)=4sin(2t),y(t)=t x(t)=4 \sin (2 t), y(t)=-t , and 0 \leq t<2 \pi ? Write your answer as a list of values of t t , separated by commas. For example, if you found t=1 t=1 or t=2 t=2 , you would enter 11,22 .

Full solution

Q. What are the critical points for the plane curve defined by the equations x(t)=4sin(2t),y(t)=t x(t)=4 \sin (2 t), y(t)=-t , and 0t<2π 0 \leq t<2 \pi ? Write your answer as a list of values of t t , separated by commas. For example, if you found t=1 t=1 or t=2 t=2 , you would enter 11,22 .
  1. Find x(t)x'(t): To find the critical points of the plane curve, we need to determine where the derivatives of x(t)x(t) and y(t)y(t) are zero or undefined. Let's start by finding the derivative of x(t)x(t) with respect to tt. The derivative of x(t)=4sin(2t)x(t) = 4\sin(2t) with respect to tt is x(t)=4cos(2t)2=8cos(2t)x'(t) = 4 \cdot \cos(2t) \cdot 2 = 8\cos(2t).
  2. Find critical points for x(t)x(t): Now, we need to find the values of tt where x(t)=8cos(2t)x'(t) = 8\cos(2t) is equal to zero within the interval 0 \leq t < 2\pi. The equation 8cos(2t)=08\cos(2t) = 0 simplifies to cos(2t)=0\cos(2t) = 0. The cosine function is zero at π/2\pi/2 and 3π/23\pi/2 within one period of the cosine function. Since we have 2t2t inside the cosine function, we divide these values by 22 to find the corresponding tt values. So, tt00 and tt11 are the points where tt22 is zero.
  3. Find y(t)y'(t): Next, we find the derivative of y(t)y(t) with respect to tt. The derivative of y(t)=ty(t) = -t with respect to tt is y(t)=1y'(t) = -1. Since y(t)y'(t) is a constant and never equals zero, there are no critical points for y(t)y(t) based on its derivative.
  4. Combine critical points: Now, we combine the critical points found from the derivatives of x(t)x(t) and y(t)y(t). Since y(t)y'(t) does not contribute any critical points, we only consider the critical points from x(t)x(t). Therefore, the critical points for the plane curve are at t=π4t = \frac{\pi}{4} and t=3π4t = \frac{3\pi}{4}.

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