Respuesta :
Use the Law of Cosines, where you have a triangle with included angle of 145 degrees and sides of 16 and 18. You are then solving the equation:
d^2 = 16^2 + 18^2 - 2(16)(18)cos(145)
d^2 = 16^2 + 18^2 - 2(16)(18)cos(145)