# Math Help - Homework Help Please

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...

2. Originally Posted by KarlosK
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

$\sin^2{m} + \cos^2{m} = 1$

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