Explanation:

Let's break down the expression: sin 25° sin 65° – cos 25° cos 65°.

- This expression is in the form of the trigonometric identity for the cosine of the difference of two angles:

cos(A - B) = cos A cos B + sin A sin B

But here, it’s in a slightly different form:

sin 25° sin 65° – cos 25° cos 65° = –(cos 25° cos 65° – sin 25° sin 65°)

- This is equal to -cos(25° - 65°).

- Simplifying 25° - 65° gives -40°.

- So, the expression simplifies to -cos(-40°) = -cos(40°).

- Cosine is an even function, so cos(-40°) = cos(40°). Thus, -cos(40°) = -cos(40°).

- Correct Anwer is 0 as the expression simplifies to 0.

- Option:3, 0 is the right option.

- Option 3 is correct.

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