Given that sin m = 5/7 and m is in the second quadrant, what is the value of cos m?
Please show work so I can understand this problem...
method 1 ...
use the Pythagorean identity
$\displaystyle \sin^2{m} + \cos^2{m} = 1$
sub in the value of sin(m) and solve for cos(m). remember that cosine < 0 in quad II
method 2 ...
sketch a reference right triangle in quad II ... label the opposite side 5 and the hypotenuse 7. use Pythagoras to calculate the length of the adjacent side.
cos(m) = (adjacent side)/(hypotenuse) ... remember cos(m) < 0