How do I prove that [math]\frac{\sin190° \cos 225° \tan 390° }{\cos 100° \sin 135°} = -\left(\frac{1}{3}\right)^{\frac{1}{2}}?[/math]
How do I prove: [math]\displaystyle \frac{\sin x - \cos x}{\sin x+\cos x} = \tan^2{\frac{x}{2}}[/math]?