Question

how to find the values of cos 135 or cos 145 or sin 105 or tan 145 etc.. means the angle which r greater than 90 degree?

Answer 1

With these simple formulas it is easy to know the value of an angle sinx=cos(90∘−x)

cosx=sin(90∘−x)

tanx=cot(90∘−x)

cotx=tan(90∘−x)

secx=cot(90∘−x)

cotx=sec(90∘−x)

1/sinx=1/cosx= sinx

1/cosx= secx

1/secx= cosx

1/tanx= cotx

1/cotx= tanx

Cos 135= Cos(90-135)=-sin 45=-sqroot of 2 divided by 2

we can answer any question this way.