## kaylala 2 years ago topic: PROVING IDENTITIES (SEE COMMENTS) (trigonometry)

1. kaylala

$[(\sec C-1)\div(\sec C +1)]=[(1-\cos C)\div(1+\cos C)]$

2. hartnn

just one identity, sec C = 1/cos C

3. hartnn

rest is just algebraic simplification

4. kaylala

you have to prove it.. like there'd be a solution or way it will turn out to be equal @hartnn

5. hartnn

thats correct, take the left side (sec C -1)/ (sec C+1) now since sec C = 1/cos C replace every sec C on left side by 1/cos C thats the first step what do u get ?

6. kaylala

i really don't get what you mean @hartnn

7. hartnn

to prove that identity , we need to prove that left side = right side. so we take left side, (sec C -1)/ (sec C+1) we can now use all the known identities here, the one which will be useful here will be sec C = 1/ cos C so, we get our first step as, (1/cos C -1)/(1/cos C +1) does this make sense ?

8. dumbcow

@hartnn already showed you what to do...are you having trouble with simplifying the fractions?

9. kaylala

oh i see now did i do it right?

10. kaylala

but my BIG question is how do you do it? you know, how to start the process and know that this identity is the one that should be used... and not the others. any tip? @hartnn @dumbcow