Answer:
The range of x values for which y is unique is 2·π
Step-by-step explanation:
For a function j: X → Y to be invertible, we have that for every y in Y, there is associated only one x which is an element of x
Hence, f(x) = cos(x - π/4) gives
the x intercept at two penultimate points of the graph of cos(x - π/4) are;
x = 2.36, and x = 8.64
x = 3/4·π, and x = 2.75·π = 
Hence the range of x values for which y is unique is presented as follows

The range of x values for which y is unique = 2·π.
Answer:
0.68865278
Step-by-step explanation:
3.4444444444444444444444444444
Step-by-step explanation:
We have xy = 28, x² + y² = 65 and x³ + y³ = 407.
Since (x + y)(x² - xy + y²) = x³ + y³,
x + y = (x³ + y³)/(x² + y² - xy)
= (407) / [(65) - (28)]
= 407 / 37
= 11.
Hence the sum of the numbers is 11.