Final answer:
The expression sin²(x) + cos²(x) is a trigonometric identity known as the Pythagorean Identity, which states that sin²(x) + cos²(x) = 1.
Step-by-step explanation:
The expression sin²(x) + cos²(x) is a trigonometric identity known as the Pythagorean Identity. It states that the sum of the squares of the sine and cosine functions of an angle x is equal to 1.
Therefore, sin²(x) + cos²(x) = 1.
So, the correct answer is option C) 1.