Hi! I want to have precision about co-functions in trigonometry.
As I know, cos(90-theta)= sintheta; cos(180-theta)=-costheta;
My question is, what's the answer for cos or sin(270-theta),
cos or sin(450-theta)?
Thank you very much
So far what you know is correct. So I underatand that you are looking for the angles 270 and 450. Well since 270 is the (-) y-axis you could use your relationships that you understand for 90 which is the (+) y-axis.
Since cos (90-`theta)=sintheta`
then cos (270-`theta)= -sintheta`
then sin(270-`theta)= -costheta`
Since 450 degrees is a coterminal angle for 90 degrees (90+360=450)