Question: an isosceles triangle with its 90 degree vertex at the...

An isosceles triangle with its 90 degree vertex at the origin has two legs of length 1 meter, one along the +x-axis and one along the +y-axis. An observer passes by, moving in the +x direction with speed 0.8c. A.) draw and label a diagram showing the triangles shape, side lengths, and angles as seen by the observer. B.) derive a general expression for how an angle to the x axis transforms from one Lorentz frame to another