Which of the following is equivalent to [tex]\cos \left(23^{\circ}\right)[/tex]?

A. [tex]\sin \left(23^{\circ}\right)[/tex]
B. [tex]\cos \left(67^{\circ}\right)[/tex]
C. [tex]\sin \left(67^{\circ}\right)[/tex]
D. [tex]\cos \left(90^{\circ}\right)[/tex]



Answer :

To determine which of the given options is equivalent to [tex]\(\cos(23^\circ)\)[/tex], we can use trigonometric identities. One of the most useful identities in this context is the co-function identity, which relates the sine and cosine functions:

[tex]\[ \sin(90^\circ - \theta) = \cos(\theta) \][/tex]

Here, [tex]\(\theta\)[/tex] is the angle we are considering. We want to find an equivalent expression for [tex]\(\cos(23^\circ)\)[/tex].

1. Using the co-function identity:
[tex]\[ \cos(23^\circ) = \sin(90^\circ - 23^\circ) \][/tex]

2. Simplify the expression inside the sine function:
[tex]\[ \cos(23^\circ) = \sin(67^\circ) \][/tex]

Therefore, [tex]\(\cos(23^\circ)\)[/tex] is equivalent to [tex]\(\sin(67^\circ)\)[/tex].

Now let's compare this with the given options:
- [tex]\(\sin(23^\circ)\)[/tex]
- [tex]\(\cos(67^\circ)\)[/tex]
- [tex]\(\sin(67^\circ)\)[/tex]
- [tex]\(\cos(90^\circ)\)[/tex]

From our step-by-step solution:
[tex]\[ \cos(23^\circ) = \sin(67^\circ) \][/tex]

Hence, the correct answer is:

[tex]\[ \sin(67^\circ) \][/tex]