Final answer:
To find the exact value of sin 140 degrees cos 20 degrees-cos 140 degrees sine 20 degrees, we can use trigonometric identities and the values of sine and cosine for 140 degrees and 20 degrees.
Step-by-step explanation:
To find the exact value of sin 140 degrees cos 20 degrees-cos 140 degrees sine 20 degrees, we can use trigonometric identities and the values of sine and cosine for 140 degrees and 20 degrees. We can rewrite the expression as:
sin 140° cos 20° - cos 140° sin 20°
Using the values of sine and cosine for 140° and 20°, we can substitute these values into the expression and simplify to find the exact value.