Simplify the expression: sin (2x) cos (5x) − sin (5x) cos (2x).
a. cos(-3x)
b. cos(7x)
c. sin(-3x)
d. sin(7x)

Respuesta :

Given:

The given expression is [tex]sin (2x) \ cos (5x) - sin (5x) \ cos (2x)[/tex]

We need to determine the simplified value of the given expression.

Simplification:

Since, the given expression is in the form of [tex]sin a \ cos b-\cos a \ sin b[/tex], the given expression can be simplified using the identity [tex]\sin (a-b)=\sin a \cos b-\cos a \sin b[/tex]

Comparing the given expression with the identity, we get;

[tex]a=2x[/tex] and [tex]b=5x[/tex]

Using this in the identity, we get;

[tex]sin (2x) \ cos (5x) - sin (5x) \ cos (2x)=sin(2x-5x)[/tex]

Simplifying, we get;

[tex]sin (2x) \ cos (5x) - sin (5x) \ cos (2x)=sin(-3x)[/tex]

Thus, the simplified value of the given expression is [tex]sin (-3x)[/tex]

Hence, Option c is the correct answer.

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