How do i find the exact value of sin(-pi/8)? I understand that sin (-pi/4) for example is -sqrt2/2
C carebear New member Joined Aug 30, 2010 Messages 45 Nov 21, 2010 #1 How do i find the exact value of sin(-pi/8)? I understand that sin (-pi/4) for example is -sqrt2/2
G galactus Super Moderator Staff member Joined Sep 28, 2005 Messages 7,216 Nov 21, 2010 #2 One way is to express it in terms of one we know. Perhaps use the identity \(\displaystyle sin(\frac{x}{2})=\pm\sqrt{\frac{1-cos(x)}{2}}\) Let \(\displaystyle x=\frac{\pi}{4}\) We know from the unit circle that \(\displaystyle cos(\frac{\pi}{4})=\frac{1}{\sqrt{2}}\)
One way is to express it in terms of one we know. Perhaps use the identity \(\displaystyle sin(\frac{x}{2})=\pm\sqrt{\frac{1-cos(x)}{2}}\) Let \(\displaystyle x=\frac{\pi}{4}\) We know from the unit circle that \(\displaystyle cos(\frac{\pi}{4})=\frac{1}{\sqrt{2}}\)
