Question

Verify the identity. sin (x + pi/2) = cos x

Answer 1

do you know a standard relation for sin (a+b) ?

Answer 2

\(\sin (a+b)=\sin a \cos b +\cos a \sin b\)

Answer 3

just plug in a =x and b =pi/2 there!

Answer 4

what does cos(pi/2) and sin(pi/2) =?

Answer 5

oh, its easy and standard
cos (pi/2) = 0
sin (pi/2) = 1

Answer 6

So I end up with sin x + cos x + sin (1)?

Answer 7

no...show your work, i'll spot you the error

Answer 8

sin(x)cos(pi/2) + cos(x)sin(pi/2)
sin(x)cos(0) + cos(x)sin(1)
cos(0) = 0 So,
sin(x) + cos(x)sin(1)
?

Answer 9

sin(x)cos(pi/2) + cos(x)sin(pi/2)
cos pi/2 = 0 , sin pi/2 = 1

sin x (0) + cos x (1)
=0+ cos x = cos x
got it?!

Answer 10

ask if any doubts...

Answer 11

Oh!! I feel dumb now. I get it. Aha Thank you!! :)

Answer 12

welcome ^_^