Quiz about Kiểm tra công thức lượng giác lần 1

Question 1

$$\sin x+\cos x=$$

Accepted Answer

$$\sqrt[]{2}\ \sin\left(x+\frac{\pi}{4}\right)$$

Answer

$$\frac{\sin x}{2\ }.\cos x\ $$

Answer

$$-\sqrt[]{2}\ \sin\left(x-\frac{\pi}{4}\right)$$

Answer

2sinx.cosx

Question 2

sina+sinb=

Accepted Answer

$$2\sin\left(\frac{a+b}{2}\right)\cos\left(\frac{a-b}{2}\right)$$

Answer

$$2\cos\left(\frac{a+b}{2}\right)\sin\left(\frac{a-b}{2}\right)$$

Answer

$$2\cos\left(\frac{a+b}{2}\right)\cos\left(\frac{a-b}{2}\right)$$

Answer

$$2\sin\left(a-b\right)\sin\left(a+b\right)$$

Question 3

cos2a=

Accepted Answer

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

Answer

$$2\cos a.\sin a$$

Answer

$$2\cos a+1$$

Answer

$$2\sin\left(a-b\right)\sin\left(a+b\right)$$

Question 4

cos2a+cos4a

Accepted Answer

$$2\cos a.\cos3a$$

Answer

$$2\cos3a.\sin2a$$

Answer

$$2\cos a.\sin3a$$

Answer

$$2\sin\left(a-b\right)\sin\left(a+b\right)$$

Question 5

cos2a.cos4a

Accepted Answer

$$\frac{1}{2}\left(\cos6a+\cos2a\right)$$

Answer

$$2\cos a.\sin3a$$

Answer

$$2\sin2a.\sin6a$$

Answer

$$\frac{1}{2}\cos6a.\cos2a$$

Question 6

cos(a+b)=

Accepted Answer

cosa.cosb-sina.sinb

Answer

$$2\cos\left(a+b\right).\cos\left(a-b\right)$$

Answer

$$2\cos\left(\frac{a+b}{2}\right).\cos\left(\frac{a-b}{2}\right)$$

Answer

cosa.cosb+sina.sinb

Question 7

sin(a+b).cos(a+b)

Accepted Answer

$$\frac{1}{2}\sin\left(2a+2b\right)$$

Answer

$$\frac{\cos2\left(a+b\right)}{2}$$

Answer

$$2\cos\left(\frac{a+b}{2}\right).\cos\left(\frac{a-b}{2}\right)$$

Answer

$$\frac{1}{2}\sin\left(2a+b\right)$$

Question 8

tan2a

Accepted Answer

$$\frac{2 an a}{1- an^2a}$$

Answer

$$\frac{\cos2\left(a+b\right)}{2}$$

Answer

$$\frac{ an a}{1- an^2a}$$

Answer

$$\frac{1}{2}\sin\left(2a+2b\right)$$

Question 9

$$\frac{\cos2a}{1+\sin2a}$$

Accepted Answer

$$\frac{\cos a-\sin a}{\cos a+\sin a}$$

Answer

$$\frac{\cos2\left(a+b\right)}{2}$$

Answer

$$\frac{ an a}{1- an^2a}$$

Answer

$$\frac{\cos a+\sin a}{\cos a-\sin a}$$

Question 10

2sin2a.cos2a

Accepted Answer

$$\sin4a$$

Answer

$$\sin2a$$

Answer

$$\frac{1}{2}\sin4a$$

Answer

$$\frac{1}{2}\sin2a$$

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