Trig questions. Which ones are true.

[shiri]

Which of the following are true?

a) sin (theta − [pi/2]) = sin (theta)
b) (sin [pi/3])(cos [pi/8]) = (sin [(3pi)/8])(cos [(3pi)/8])
c) sin (theta + theta) = sin (2theta)
d) (sin [2theta])/(sin [3theta]) = 2/3

a) F
b) F
c) T
d) T

Tell me I got the right answers, please.

 

[Mark44]

d is wrong. b looks right, but I would want to check it, just to be safe. The others are right.

 

[GSXR1000]

If you have a graphing calculator you can graph both equation to verify they are equal.

 

[GSXR1000]

a: pi/2 is just the phase shift. Will pi/2 make them out of phase?

b: with no variable (Theta) plug and chug in the calculator unless you teacher wants you to prove?

c: does does x+x=2x?

d: when Theta =? or maybe I should say will it for any Theta.