Evaluate `sinthetacos(90^(@)-theta)+costhetasin(90^(@)-theta)`.

Answer

To evaluate the expression \( \sin \theta \cos(90^\circ - \theta) + \cos \theta \sin(90^\circ - \theta) \), we can follow these steps:

### Step 1: Use Trigonometric Identities
We know from trigonometric identities that:
- \( \cos(90^\circ - \theta) = \sin \theta \)
- \( \sin(90^\circ - \theta) = \cos \theta \)

### Step 2: Substitute the Identities
Substituting these identities into the expression gives us:
\[ \sin \theta \cdot \sin \theta + \cos \theta \cdot \cos \theta \]

### Step 3: Simplify the Expression
This simplifies to:
\[ \sin^2 \theta + \cos^2 \theta \]

### Step 4: Apply the Pythagorean Identity
We know from the Pythagorean identity that:
\[ \sin^2 \theta + \cos^2 \theta = 1 \]

### Final Result
Thus, the value of the original expression is:
\[ 1 \]