Question

which of the following are identities A. cos(x+pi/6)=-sin(x-pi/3) B. 1-tanxtany+sin(x+y)/sinxsiny C. tanx-tany+sin(x-y)/cosxcosy D. tan(x-pi/4)=tanx-1

Answer 1

cos(x+pi/6)=-sin(x-pi/3) is true since cos(x)=sin(x+pi/2)

Answer 2

there is two answers

Answer 3

@marissak Option C is not an equation. Where is the = symbol?

C) tanx-tany+sin(x-y)/cosxcosy

Answer 4

sorry, its suppose to be tanx-tany=sin(x-y)/cosxcosy

Answer 5

@marissak Same question for option B

Answer 6

and B is suppose to be 1-tanxtany=sin(x+y)/sinxsiny

Answer 7

@marissak >> Why do you say this: there is two answers

Answer 8

@directrix because its a choose all that apply question. they usually have two answers

Answer 9

I agree with @Prebz on cos(x+pi/6)=-sin(x-pi/3) is true @marissak
I don't agree that there must be another answer but there could be.

Answer 10

Okay thank you

Answer 11

What I'm wondering is if all the grouping symbols are shown in the options.

B) 1-tanxtany=sin(x+y)/sinxsiny
Same as:
1 - (tanx)(tany) = [sin(x + y)] / [sin(x)*sin(y)] ?

Answer 12

i just rechecked them and they are the same as i typed them

Answer 13

@marissak I am sticking with @Prebz

A) cos(x+pi/6)=-sin(x-pi/3) is true FINAL ANSWER (Best final answer I see)

Answer 14

haha okay thank you so much

Answer 15

@marissak Let us know the answer

Answer 16

okay i will. i have 4 more questions to go and then it'll tell me if it was right or wrong