If under the standard position you think that the first arm (side) belongs to the positive direction of the x axis and the second one passes through a given point then it is:
if we form a right triangle with sides 3 and 4 then the hypotenuse is 5.
sin Θ = 4/5 and cos Θ = - 3/5
we know that the formula for double the value of the angle is:
