Question

anybody know how to verify the identity? I've never done this before and my text don't cover this. i never learned this in actual school either so i need help from somebody who does.

Answer 1

What do you mean by verifying an identity? You mean you need a proof? Or a derivation?

Answer 2

I might start with cot x = cos x / sin x and tan x = sin x /cos x and then see how these behave for angle offset by pi/2.

Answer 3

i would do it as advised:
\[\large \cot(x-\pi/2)=\frac{\cos(x-\pi/2)}{\sin(x-\pi/2)}= \]
\[\large =\frac{\cos x\cos(\pi/2)+\sin x\sin(\pi/2)}
{\sin x\cos(\pi/2)-\sin(\pi/2)\cos x}=
\frac{\sin x}{-\cos x}=-\tan x \]

Answer 4

@helder_edwin Can you please explain how did you get cos(x - pi/2) = cosxcos(pi/2) +sinx(sinpi/2)?

Which property did you use?

Answer 5

it is a tryg identity:
\[\large \cos(x-y)=\cos x\cos y+\sin x\sin y \]

Answer 6

and what property did you use to get to the step before the last?

Answer 7

@helder_edwin

Answer 8

\[\large \cos(\pi/2)=0 \]
\[\large \sin(\pi/2)=1 \]

Answer 9

it is the demonstration of the identity u posted.

Answer 10

Okay thank you i just wanna make sure. (:

Answer 11

what?how? i cant lol

Answer 12

thanks :)

Answer 13

You're welcome.

Answer 14

I still need help if anybody is willing to help meeee

Answer 15

Hi!

Answer 16

Hey! lol

Answer 17

lol

Answer 18

:D