Final answer:
The equation sin((π/2) - x) = cos x has x that can be any real number since the identity holds true for all real numbers.
Step-by-step explanation:
The equation that is provided, sin((π/2) - x) = cos x, is an identity called the co-function identity.
The co-function identity states that sin(θ) = cos(90° - θ) and vice versa.
Thus, sin ((π/2) - x) is equivalent to cos x.
Therefore, x can be any angle that satisfies this identity.
In other words, x can be any real number, because for every value of x, there will always be a corresponding value of sin ((π/2) - x) that equals cos x due to the periodic nature of trigonometric functions.