Question

sin a= 3/5 and is in quadrant II
cos b = 2/5 and is in Quadrant I Find Cos (a-b)

Answer 1

yo yo yo i still dont know how to do

Answer 2

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

Answer 3

sin b is positive (in first quad), cos a is neg (in second quad)

Answer 4

use pythag to find co functions (if needed)

Answer 5

wait so what is cos a and what is sina and sin b

Answer 6

remember \[\cos ^{2}x+\sin ^{2}x=1\]

Answer 7

ok

Answer 8

but what is it?

Answer 9

sin a = 3/5, cos a < 0, so

\[\cos a=-\sqrt{1-\left( \frac{ 3 }{ 5 } \right)^{2}}\]