Question

α 11. seca - tana = cot(π÷4+a÷2) ​

Answer 1

Step-by-step explanation:

((1-sina)÷(Cosa))

sina = 2 sin(a/2) cos(a/2);

cosa = (cos(a/2)+sin(a/2))x(cos(a/2)-sin(a/2))

1-sina = (cos(a/2))^2 + (sin(a/2))^2 - 2 sin(a/2) cos(a/2);

1 - sina = (cos(a/2)-sin(a/2))^2

so ((1-sina)÷(Cosa)) = (cos(a/2)-sin(a/2)) ÷ (cos(a/2)+sin(a/2))

which is equal to (cot(a/2)-1) ÷ (cot(a/2)+1)

which is the expansion of cot(π÷4+a÷2)