Question

Find sin (x+y), assuming that sin x= -2/3, cos y=1/4 and both x and y are in quadrant IV.

Answer 1

sin(x+y)=sinxcosy+cosysinx

Answer 2

are you familiar with this identity?

Answer 3

no

Answer 4

i have to look at my notes

Answer 5

do you know how to find cos(x) if you are given sin(x)? because you need that too.

Answer 6

sin x=1/cos x

Answer 7

This is incorrect I think you are mistaking it with
sec(x)=1/cos (x)

Answer 8

oh, you're right

Answer 9

Okay, so we know this identity
sin(x+y)=sin(x)cos(y)+cos(y)sin(x)
now we have to plug in what we know

Answer 10

You know
sin(x),cos(y)
you don't know
sin(y),cos(x)

Answer 11

i have no idea what to do

Answer 12

So you need to find what you don't know
are you familiar with soh-cah-toa

Answer 13

a bit, but I don't even know how you got sin (x+y)=sin (x)cos(y)+cos(y)sin(x)

Answer 14

this is identity, you just need to know that

Answer 15

ok, I see it in my notes under cosine of a sum or difference