a) Sketch the graphs of y= tanA and y= secA

b) Prove that secA- tanA= 1 / (secA+tanA)

c) Deduce from parts a) and b) that secA-tanA is greater than 0 and less and equal to 1,

for values of A such that A is greater and equal to 0 and less than and equal to 90 degrees. Explain your reasoning clearly.

d) Given that secA-tanA= 1/2

find the exact value of cosA