Question

If sec a = 5/4 and a is an angle in quadrant iv find the value of cos a

Answer 1

we know that
sec a = 5/4
sec(a)=1/cos(a)
then 
cos (a)=1/sec(a)
cos (a)=1/(5/4)=4/5---> is positive because the function cos is positive in IV quadrant

the answer is cos(a)=4/5