1. Công thức lượng giác

$$\frac{\pi}{6}$$  

$$\frac{\pi}{3}$$  

$$\frac{\pi}{4}$$  

$$\frac{\pi}{2}$$  

sina.sinb + cosa.cosb

sina.cosb + cosa.sinb

sina.cosb - cosa.sinb

sina.sinb - cosa.cosb

cosa.sinb - sina.cosb

cosa.sinb - sina.cosb

cosa.cosb + sina.sinb

cosa.sinb + sina.cosb

sin2a

cos2a

tan2a

cot2a

2sin²a-1

1-2cos²a

1-sin²a

cos²a-sin²a

2cos $$\frac{a+b}{2}$$ cos $$\frac{a-b}{2}$$

2sinundefined cosundefined

2cosundefined sinundefined

2sinundefined sinundefined

sina.sinb

cosa.sinb

sina.cosb

cosa.cosb

$$\sqrt{2}$$ sin( x - $$\frac{\pi}{4}$$ )

undefined sin( x +undefined )

undefined cos( x -undefined )

undefined cos( x +undefined )

$$\sin^2a+\cos^2a=1$$

$$1+\tan^2a=\frac{1}{\cos^2a}$$

$$1+\cot^2a=\frac{1}{\sin^2a}$$

$$\tan a+\cot a=1$$

$$30^o$$  

$$45^o$$  

$$60^o$$  

$$120^o$$  

$$\frac{\sqrt{6}+\sqrt{2}}{4}$$  

$$\frac{\sqrt{6}-\sqrt{2}}{4}$$  

$$-\frac{\sqrt{6}+\sqrt{2}}{4}$$  

$$\frac{\sqrt{2}-\sqrt{6}}{4}$$  

$$\frac{1}{2}$$  

$$\sqrt{2}$$  

$$\frac{\sqrt{2}}{2}$$  

$$-\sqrt{2}$$  

$$\frac{\sin x}{\cos x}$$  

$$\frac{\sin a}{\cos a}$$  

$$\frac{\sin2x}{\cos2x}$$  

$$\frac{\sin2a}{\cos2a}$$  

$$\sin^2x-\cos^2x=1$$

$$\sin^2x+\cos^2x=1$$

$$\sin^2x=1+\cos^2x$$

$$\cos^2x=\sin^2x-1$$

$$1+\cos^2x=\frac{1}{\tan^2x}$$

$$1-\cos^2x=\frac{1}{\tan^2x}$$

$$1+\tan^2x=\frac{1}{\cos^2x}$$

$$1-\tan^2x=\frac{1}{\cos^2x}$$

$$\cos\left(a+b\right)=\cos a.\cos b+\sin a.\sin b$$

$$\cos\left(a+b\right)=\cos a.\cos b-\sin a.\sin b$$

$$\cos\left(a+b\right)=\sin a.\cos b+\cos a.\sin b$$

$$\cos\left(a+b\right)=\sin a.\cos b-\cos a.\sin b$$

$$\sin\left(a-b\right)=\cos a.\cos b-\sin a.\sin b$$  

$$\sin\left(a-b\right)=\cos a.\cos b+\sin a.\sin b$$

$$\sin\left(a-b\right)=\sin a.\cos b-\cos a.\sin b$$

$$\sin\left(a-b\right)=\sin a.\cos b+\cos a.\sin b$$

$$2.\sin a.\cos a$$  

$$2.\sin2a.\cos2a$$  

$$2.\sin4a.\cos4a$$  

$$1-\cos^24a$$  

$$\cos2a=2\cos^2a-1$$

$$\cos2a=1-2\sin^2a$$

$$\cos2a=\sin^2a-\cos^2a$$

$$\cos2a=\cos^2a-\sin^2a$$

$$2\cos4a.\cos2a$$  

$$2\cos8a.\cos4a$$  

$$2\sin8a.\sin4a$$  

$$-2\sin4a.\sin2a$$