9. Given cot(a)= 6/5 and cos(B)= 4/7 for a third-quadrant angle (a) and a fourth-quadrant angle (B), use the Definition of Trigonometrie Functions of Any Angle to find the exact value for cos((a)+(B)). Show the formula you are using in your work. Notice that the "SOHCAHTOA" method does not apply here. The angles (a) and (B) are not acute angles inside of a right triangle. Apply the Definition of Trigonometrio Functions of Any Angle.