Given that cos a = 3/5 and it is in the first quadrant : then: a=arccos 3/5 but cot θ=1/tan θ thus to evaluate our vale we shall obtain the value for height since adjacent=3 hypotenuse=5 thus using Pythagorean theorem: c²=a²+b² hence 5²=3²+b² b²=25-9=16 b=4 thus tan θ=opposite/adjacent tan a=4/3 thus cot a=1/(4/3)=3/4
