The correct answer is letter A. star. <span>A ball of gas becomes a STAR when nuclear fusion begins in its core.</span>
To convert parametric to Cartesian systems, you need to find a way to get rid of the t's.
In this case, the t's are inside trigonometric functions, so we're going to use a very famous trig identity you should memorize:

If we plug sin(t) and cos(t) into that equation only x and y variables will be left!
BUT there's one thing. The given cos(t + pi/6) has nasty extra stuff in it. However, part a gives you a tip on how to relate x and y to a nice clean cos(t)
So if we do a little rearranging:

Now we can plug these into the famous trig identity!

Do a little bit of adjustments to get that final form asked for, and you'll be able to find those integers of a and b. ;)
Answer:
The width of the river is 
Explanation:
From the question we are told that
The distance of the base line is D = 130 m
The angle is 
A diagram illustration the question is shown on the first uploaded image
Applying Trigonometric Rules for Right-angled Triangle,

Now making z the subject


The process that causes liquid rock to move is called convection