Which of the following are identities? check all that apply. a) tan x - tan y = sin(x-y)/cosxcosy b) 1 - tanxtany = sin(x+y)/sinxsiny c) tan(x-pie/4) = tanx-1 d) cos(x+pie/6) = -sin(x-pie/3)

The correct answer option is a) tan x - tan y = sin(x-y)/cosxcosy.

Step-by-step explanation:

The option a) tan x - tan y = sin(x-y)/cosxcosy is an identity. Let us prove it:

The right side is equal to:

which is equal to the left side.

Hence, tan x - tan y = sin(x-y)/cosxcosy is an identity.

While rest of the options do not equal to each of their sides so they are not identities.

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step-by-step explanation:

a

b

d

step-by-step explanation: