Question

Proving identities.

Answer 1

cos(x-pi/2) = sinx

Answer 2

@Nnesha :))

Answer 3

ai ai ai

Answer 4

ok well I recognize that it has an identity. Subraction formula.

Answer 5

cos(a-b)= cosa cos b +sina sinb

Answer 6

so in our case it's
cos(a-b) = cos(x) cos(pi/2) + sin(x)sin(pi/2)

Answer 7

oh proving identities means that you make the sides equal each other. So we need to prove that cos(x = pi/2) is equivalent to sinx

Answer 8

haha you want to go to sleep? :)

Answer 9

aw thank you!

Answer 10

sleep happy ^-^

Answer 11

I'll just slaaave away for a few more.

Answer 12

Basically what we have is :cos(a-b) = cos(x) cos(pi/2) + sin(x)sin(pi/2)

Answer 13

yeah its sinx

Answer 14

er, yeah. I need to show how to get there, which i'm not quite sure about..

Answer 15

how did you reach that?

Answer 16

okay
tell me what's cos (pi/2)

Answer 17

0

Answer 18

yeah
so the first term becomes 0

Answer 19

what's sin(pi/2)=?

Answer 20

1

Answer 21

does all of cos(x) and cos (pi/2) become zero?

Answer 22

well 0 X any number is what ?

Answer 23

0 :P

Answer 24

so it becomes 0

Answer 25

I see, haha ok. and when sin(1) we can just leave it out?
so only sinx is left

Answer 26

:)
All the best!!!

Answer 27

Thank you so much!