Question

DANGER! need help! please?
please help! crashing for finals!
find cos(u+v) given that sin u=3/5 and cos v=-5/13 (both u and v are in Quad 2

Answer 1

please help?

Answer 2

\[ \cos(u+v) = \cos(u) \cos(v) - \sin(u) \sin(v)
\]

Answer 3

\[
\cos^2(u)= 1 - \frac 9{25}= \frac {16}{25}
\]

Answer 4

\[
\sin^2(v)= 1 - \frac {25}{169}= \frac {144}{169}
\]

Answer 5

Can you finish it?

Answer 6

i having a little trouble can u explain what u just did please? step-by-step?

Answer 7

Be careful u and v are in quadrant 2

Answer 8

I used
\[
\cos^2(x) + \sin^2(x) =1
\]

Answer 9

okay so u used this formula and plugged in the values?

Answer 10

that were given?

Answer 11

yes

Answer 12

okay so it'll be cos^2(x)+sin^2(x)=1 and the i plug in the given info so it''l be cos^2(-5/13)+sin^2(3/5)=1?

Answer 13

you should obtain
\[
\cos(u) = -\frac 4 5\\
\sin(u) =\frac {12}{13}
\]

Answer 14

how?