Question

Verify the Identity cos(α - β) - cos(α + β) = 2 sin α sin β
@Nnesha

Answer 1

cos=1/sec

Answer 2

1/sec(a-b)-1/sec(a+b)=2sin(a) sin(b)

Answer 3

i cant read what you wrote lol

Answer 4

why do i have a feeling everything iv learned about verifying so far will not help me here

Answer 5

cos(α - β) = cosα cosβ + sinα sin β
cos(α + β) = cosα cosβ - sinα sin β

These are two rules which you must know :) They're known as your addition and subtraction (or sum and difference) formulas for cosine

Answer 6

uhhhh i see a bunch of question marks on my screen^

Answer 7

trigo is important

Answer 8

refresh your page

Answer 9

wait\[\cos(a+b)=cosacosb-sinasinb\]
\[\cos(a-b)=cosacosb+sinasinb\]

Answer 10

yyaasss :D So those are the two formulas you need to remember @quick24

Answer 11

ok

Answer 12

can yall give me like 3 minutes i need a smoke break

Answer 13

for cos
its opposite signs
whereas for sine its the same sign

t\[\sin(a+b)=sinacosb+cosasinb\]

\[\sin(a-b)=sinacosb-cosasinb\]

Answer 14

ok im backn @rvc @butterflydreamer

Answer 15

hey rvc

Answer 16

so u got those formulas?

Answer 17

i havent copied them yet but i will

Answer 18

do it pls

Answer 19

i copied cos(a+b)=cosacosb−sinasinb
and cos(a−b)=cosacosb+sinasinb r those the ones i need

Answer 20

@rvc

Answer 21

yes

Answer 22

so now what

Answer 23

what u need?

Answer 24

i need to verify L.H.S=R.H.S

Answer 25

can you walk me through it and yes i will do the lifting just need you to give me hints in the right direction

Answer 26

yes
what help u need

Answer 27

just start from the begging and explain what i have to do like how to apply those formulas for instance

Answer 28

well what grade r u in?

Answer 29

12th

Answer 30

so that i may direct u in the right way

Answer 31

im a senior

Answer 32

no

Answer 33

why

Answer 34

okay
just to get a idea what kinda questions u may get

Answer 35

im white in america and im a senior

Answer 36

hmm..
look
to start with
u may gett this to prove lhs or rhs

Answer 37

im to prove rhs im assuming as thats what i had to do in the other verification problem

Answer 38

oh

Answer 39

expand the LHS @quick24

Answer 40

so plug in that equation to replace the L.H.S terms

Answer 41

yes!

Answer 42

show the working @quick24

Answer 43

ok so its
(cos(a)*cos(b)+sin(a)*sin(b))-(cos(a)*cos(b)-sin(a)*sin(b))

Answer 44

[(\cos(a)*\cos(b)+\sin(a)*\sin(b)) - (\cos(a)*\cos(b)-\sin(a)*\sin(b)\]

Answer 45

\[(\cos(a)*\cos(b)+\sin(a)*\sin(b))-(\cos(a)*\cos(b)-\sin(a)*\sin(b))\]

Answer 46

hey
since its has angles alpha and beta use them instead of a nd b

Answer 47

now open the brackets

Answer 48

will you still be on in about 30 minutes i have to drive my grandmother somewhere

Answer 49

rvc?

Answer 50

okay

Answer 51

thank

Answer 52

@rvc hey