Find curve of intersection, tangent line, and point on helix

[mercedesbenz]

please help me, I try to do but i can not.

1. Find a vector function $$F(t)$$ whose graph is the curve of intersection of
$$z=\sqrt{4-x^2-y^2}$$ and $$y=x^2$$.

2. Find parametric equations for the line that is tangent to the curve $$r(t)=(e^t)i+(sin t)j+\ln(1-t)k$$ at t=0.

3. Find the point on the curve $$r(t)=(12sin t)i-(12cos t)j+(5t)k$$
at a distance $$13\pi$$ units along the curve from the origin in the direction opposite to the direction of increasing arc length.

 

[HallsofIvy]

I'm glad to hear you tried. Please show WHAT you tried so we can we will know what suggestions will help you.