For what value of [tex]x[/tex] is [tex]\cos (x) = \sin (14^{\circ})[/tex], where [tex]0^{\circ} \ \textless \ x \ \textless \ 90^{\circ}[/tex]?

A. [tex]28^{\circ}[/tex]
B. [tex]76^{\circ}[/tex]
C. [tex]31^{\circ}[/tex]
D. [tex]14^{\circ}[/tex]



Answer :

To find the value of [tex]\( x \)[/tex] for which [tex]\(\cos(x) = \sin(14^\circ) \)[/tex] within the range [tex]\( 0^\circ < x < 90^\circ \)[/tex], we can use a fundamental trigonometric identity.

The identity states that:
[tex]\[ \sin(\theta) = \cos(90^\circ - \theta) \][/tex]
for any angle [tex]\(\theta\)[/tex].

Given [tex]\(\sin(14^\circ)\)[/tex], we need [tex]\(\cos(x)\)[/tex] to be equal to [tex]\(\sin(14^\circ)\)[/tex]. Using the identity, we can write:
[tex]\[ \sin(14^\circ) = \cos(90^\circ - 14^\circ) \][/tex]

Thus, if [tex]\(\cos(x) = \sin(14^\circ)\)[/tex], we must have:
[tex]\[ x = 90^\circ - 14^\circ \][/tex]

So, calculating this gives:
[tex]\[ x = 90^\circ - 14^\circ = 76^\circ \][/tex]

Therefore, the value of [tex]\( x \)[/tex] for which [tex]\(\cos(x) = \sin(14^\circ) \)[/tex] is [tex]\( 76^\circ \)[/tex]. Hence, the correct answer is:

[tex]\[ \boxed{76^\circ} \][/tex]