Question

why sin (90°-theta) is cos theta and why sin(270-theta) is -cos theta. please give me proper explanation I am confused​

Answer 1

sin (270° - θ) = -cos θ

As 270° and 90° convert the trigonometric ratio therefore sin is converted to cos. And negative sign is due to sin (as 270° - θ lies in third quadrant where tan and cot are positive other trigonometric ratios are negative) thus from these we concluded ,

sin (270° - θ) = -cos θ