trig identities

Question 1

1/cos x

Answer 1

sec x

Question 2

1/sin x

Answer 2

csc x

Question 3

1/tan x

Answer 3

cot x

Question 4

sin 2x

Answer 4

2sinxcosx

Question 5

cos2x

Answer 5

cos^2x - sin^2x = 1-sin^2x = 2cos^2x - 1

Question 6

sin(x/2)

Answer 6

+/- sqrt((1-cosx)/2) and used for pi/8

Question 7

cos(x/2)

Answer 7

+/i sqrt((1+cosx)/2) and used for pi/8