Question 1004190
cosine theta will be equal to -4/5.


the angle will be 180 - arccos(4/5) = 143.1301024 degrees.


the equivalent angle in the first quadrant is equal to 180 - 143.1301024 degrees which is equal to 36.86989765 degrees.


the triangle is a 3/4/5 triangle in the third quadrant.


it is in the third quadrant because the adjcent side on the x-axis is negative and the opposite side on the y-axis is also negative.


the hypotenuse is always positive.


the hypotenuse is 5 because 3^2 + 4^2 = 9 + 16 = 25 and sqrt(25) = 5.


this is based on pythagorus who says that a^2 + b^2 = c^2.


a diagram of your angle is shown below:


<img src = "http://theo.x10hosting.com/2015/111701.jpg" alt="$$$" </>


the radius of your circle is 5, and so the equation of the circle becomes x^2 + y^2 = 25.