ĐGTD ĐH Bách khoa - Tư duy Toán học - Giá trị lượng giác của các góc có liên quan đặc biệt

$\cot \left(\pi -\alpha \right)=\cot \left(\pi +\alpha \right)$

$\cot \left(\frac{\pi }{2}-\alpha \right)=\tan \left(\pi +\alpha \right)$

$\cot \left(\pi +\alpha \right)=\cot \left(-\alpha \right)$

$\cot \left(\pi +\alpha \right)=\cot \left(\frac{\pi }{2}-\alpha \right)$

$\sin \left(\pi -\alpha \right)=\sin \left(\pi +\alpha \right)$

$\sin \left(\frac{\pi }{2}-\alpha \right)=\sin \left(\pi +\alpha \right)$

$\sin \left(\pi +\alpha \right)=\sin \left(-\alpha \right)$

$\sin \left(\pi +\alpha \right)=\cos \left(\frac{\pi }{2}-\alpha \right)$

$\tan \left(\pi -\alpha \right)=tan\left(\frac{\pi }{2}-\alpha \right)$

$tan\left(\frac{\pi }{2}-\alpha \right)=\tan \left(-\alpha \right)$

$tan\left(\pi -\alpha \right)=tan\left(\frac{\pi }{2}+\alpha \right)$

$tan\left(\frac{\pi }{2}-\alpha \right)=\cot \left(\pi +\alpha \right)$

$\tan \left(\pi +\alpha \right)=-tan\alpha$

$tan\left(-\alpha \right)=-\tan \left(\alpha \right)$

$tan\left(\frac{\pi }{2}-\alpha \right)=\cot \left(\alpha \right)$

$tan\left(\pi -\alpha \right)=-tan\left(\alpha \right)$

$\sin \frac{A+B}{2}=\sin \frac{C}{2}$

$\cos \frac{A+B}{2}=\cos \frac{C}{2}$

$\sin \left(A+B\right)=\sin C$

$\cos \left(A+B\right)=\cos C$

$A=\cos \alpha +\sin \alpha$

$A=2\sin \alpha$

$A=\sin \alpha -\cos \alpha$

A = 0

0

1

2

4

$\sin 225°=\frac{-\sqrt{2}}{2}$

$\cos 225°=-\frac{\sqrt{2}}{2}$

$\tan 225°=-1$

$\cot 225°=1$

2sinx

– 2 cotx

0

– 2 sinx

$-\frac{1}{3}$

$\frac{1}{3}$

$\frac{2}{3}$

$-\frac{2}{3}$

S = 1

S = 0

S = sin²x – cos²x

S = 2 sinx cosx

$\cos \frac{B+C}{2}=\sin \frac{A}{2}$

$\sin \left(A+C\right)=-\sin B$

$\cos \left(A+B+2C\right)=-\cos C$

$\cos \left(A+B\right)=-\cos C$

Chỉ I

II và III

I và II

Chỉ III