Question

How do i prove trignometric identities

Answer 1

@Zarkon

Answer 2

@Kainui

Answer 3

@brianayala

Answer 4

Proving an identity is very different in concept from solving an equation. Though you'll use many of the same techniques, they are not the same, and the differences are what can cause you problems.

An "identity" is a tautology, an equation or statement that is always true, no matter what. For instance, sin(x) = 1/csc(x) is an identity. To "prove" an identity, you have to use logical steps to show that one side of the equation can be transformed into the other side of the equation. You do not plug values into the identity to "prove" anything. There are infinitely-many values you can plug in. Are you really going to "prove" anything by listing three or four values where the two sides of the equation are equal? Of course not. And sometimes you'll be given an equation which is not an identity. If you plug a value in where the two sides happen to be equal, such as π/4 for the (false) identity sin(x) = cos(x), you could fool yourself into thinking that a mere equation is an identity. You'll have shot yourself in the foot. So let's don't do that.

To prove an identity, your instructor may have told you that you cannot work on both sides of the equation at the same time. This is correct. You can work on both sides together for a regular equation, because you're trying to find where the equation is true. When you are working with an identity, if you work on both sides and work down to where the sides are equal, you will only have shown that, if the starting equation is true, then you can arrive at another true equation. But you won't have proved, logically, that the original equation was actually true.

Answer 5

can u give an example and solve it

Answer 6

@lupita1995

Answer 7

@LmaO1 ..this might help.. http://www.intmath.com/analytic-trigonometry/1-trigonometric-identities.php

Answer 8

guys we r supposed to proove the equation using their ratios

Answer 9

Pythagorean Identities

1. cos2(θ) + sin2(θ) = 1
2. 1 + tan2(θ) = sec2(θ)
3. cot2(θ) + 1 = csc2(θ)
@LmaO1 good enough??

Answer 10

sorry i didn't help

Answer 11

yup i knw the identities but it is really confusing i dont know how to solve them

Answer 12

bye

Answer 13

Guyz pls help

Answer 14

i tried

Answer 15

i did help but i guess i cant do it

Answer 16

okay :(

Answer 17

there is no "method" for solving identities that will always work.
you have some basic identities that you use to solve more complex ones.

those basic ones have been listed at length above. the best way to get good is to practice them, which I know is not what you want to hear, but it is. If you have some examples I will gladly help, as I love them even though I used to hate them, and asked someone this very same question.

Answer 18

@ganeshie8

Answer 19

are you confused by anything I said?

Answer 20

yup

Answer 21

which part?

Answer 22

the whole part

Answer 23

ok lets start from line one

"there is no "method" for solving identities that will always work."

did this confuse you?

Answer 24

kk

Answer 25

@matricked