Question

Answer the question in the picture

Answer 1

Answer:

• left picture (bottom expression): -cot(x)
• right picture (top expression): tan(x)

Step-by-step explanation:

A graphing calculator can show you a graph of each expression, which you can compare to the offered choices.

_____

You can make use of the relations ...

... sin(a)+sin(b) = 2sin((a+b)/2)cos((a-b)/2)

... cos(a)+cos(b) = 2cos((a+b)/2)cos((a-b)/2)

... cos(a)-cos(b) = -2sin((a+b)/2)sin((a-b)/2)

Then you have ...

$\dfrac{\cos{2x}-\cos{4x}}{\sin{2x}+\sin{4x}}=\dfrac{2\sin{3x}\sin{x}}{2\sin{3x}\cos{x}}=\dfrac{\sin{x}}{\cos{x}}=\tan{x}$

and ...

$\dfrac{\cos{2x}+\cos{4x}}{\sin{2x}-\sin{4x}}=\dfrac{2\cos{3x}\cos{x}}{-2\cos{3x}\sin{x}}=\dfrac{-\cos{x}}{\sin{x}}=-\cot{x}$