Question

Find exact value if: 0 14 years ago

Answer 1

Now I KNOW I answered this question yesterday AND a few minutes ago.

Answer 2

what a answer?

Answer 3

Do you know the formula for sin(a+b)?

Answer 4

yes, but I not sure I solve it right

Answer 5

Post how you solved it. I'll tell you if it's right, or where you went wrong.

Answer 6

can you show your work?

Answer 7

Can YOU show YOUR work?

Answer 8

\[\sin\frac{4}{9}\cos\frac{1}{4}+\cos\frac{4}{9}\sin\frac{1}{4}\]

Answer 9

x doesn't equal 4/9. sin x = 4/9.

Use the sin(a+b) formula to expand sin(x-y)

Answer 10

I know you know how to do it because you did it before.

Answer 11

I don't get it

Answer 12

What's the formula for sin(a+b)?

Answer 13

\[cosx=\sqrt{1-(\frac{4}{9})^2}\]this I folow from the book

Answer 14

That's right, but first you have to expand sin(x-y). To do that you need to know the rule for expanding sin(a+b). What is the rule?

Answer 15

sin(a)cos(b)+cos(a)sin(b)

Answer 16

Correct. Now apply that formula to sin(x-y). You use the rule you just typed, but set a=x and b=-y.

Answer 17

sin(4/9)cos(-1/4) +cos(4/9)sin(-1/4)?

Answer 18

Whoa! Hold on there. Don't start substituting values just yet. Expand sin(x-y) using the sin(a+b) formula you just typed.

Answer 19

Also, x and y aren't 4/9 and 1/4. SIN x = 4/9 and SIN y = 1/4. There's a big difference.

Answer 20

how you solve?

Answer 21

Do what I asked you to do. Expand sin(x-y) using the formula you already posted for expanding sin(a+b). Use a=x and b=-y.

Answer 22

yes I did

Answer 23

You wrote sin(a+b) = sin(a)cos(b) + cos(a)sin(b). Use that formula to expand sin(x-y). Just plug in x for a and -y for b.

Answer 24

Post what you got.

Answer 25

I did post

Answer 26

sin(a+b) = sin(a)cos(b) + cos(a)sin(b).
sin(4/9)cos(-1/4) +cos(4/9)sin(-1/4)?

Answer 27

Copy and post it again, because I don't see it. It should be an expression in x and y.

Answer 28

sin(a+b) = sin(a)cos(b) + cos(a)sin(b).

sin(4/9)cos(-1/4) +cos(4/9)sin(-1/4)?

Answer 29

Neither of those are an expression in x and y.

Answer 30

Also, you don't know the values of x or y. You only know the values of sin(x) and sin(y).

Answer 31

So you need to find an expression involving sin(x), sin(y), cos(x), and cos(y) so you can plug in the values that you DO know.

Answer 32

That's why I keep asking you to use the sin(a+b) formula to expand sin(x-y). That will yield an expression involving sin(x), sin(y), cos(x), and cos(y).

Answer 33

It getting late I need go sleep,I will work on it, I f I don't get I will post again tomorrow,ty

Answer 34

sin(x - y) =sinx*cosy - cosx*siny

Answer 35

\[sin^2\theta + cos^2\theta = 1 \]

Answer 36

You can get cos values with the above identity