Answer:
To solve the equation 7cos(9x)−1=1, we first need to move the 1 to the left side of the equation:
7cos(9x) = 2
To find the solutions of the equation, we can divide both sides by 7:
cos(9x) = 2/7
Now we will use the inverse cosine function, denoted as arccos, to find the angle that has a cosine value of 2/7. Since the function cos is periodic with period 2Pi, it's range is [-1,1], we will look for the solutions between 0 and 2Pi.
x = (1/9)arccos(2/7) + (2kPi)/9 for k =0,1,2,....
we can also express the solution in degrees by multiplying the radian measure with 180/Pi.
x = (20/63)arccos(2/7) + (160*k) for k =0,1,2,....
or
x = (20/63) * arccos(2/7) * (180/pi) + (160*k) for k =0,1,2,....
where k is an integer.
So, x = (20/63) * arccos(2/7) * (180/pi) + (160*k) where k =0,1,2,.... is an expression that represents all solutions to the equation in degrees.