Show that any unit vector in R^2 can be written as (cosX, sinX). What is the angle X?

I have a vectors test coming up and i need some help. Also this is only my first test, so i don't know anything about the dot product or cross product or projections. 1.)Show that any unit vector in R^2 can be written as (cosX, sinX). What is the angle X? 2.) a.) Find the length of the median AM in the... show more I have a vectors test coming up and i need some help. Also this is only my first test, so i don't know anything about the dot product or cross product or projections.

1.)Show that any unit vector in R^2 can be written as (cosX, sinX). What is the angle X?


2.) a.) Find the length of the median AM in the triangle ABC for the points A(2, 1.5, -4), B(3, -4, 2), and C(1,3,-7).

b.) Find the distance from A to the centroid of the triangle.

3.) If Vector XQ + XY = (m-1)YQ, what conclusions can you draw?
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