Answer:
[tex]\cos \left(90 ^\circ - x\right) \approx 0.1688[/tex]
Step-by-step explanation:
We are given that:
[tex]\displaystyle \tan x = \frac{3}{7}[/tex]
And we want to find the value of:
[tex]\displaystyle \cos \left(90^\circ - x\right)[/tex]
Recall that by definition, tan(θ) = sin(θ) / cos(θ). Hence:
[tex]\displaystyle \frac{\sin x }{\cos x} = \frac{3}{7}[/tex]
And by definition, sin(θ) = cos(90° - θ). Hence:
[tex]\displaystyle \frac{\cos \left(90^\circ - x\right)}{\cos x} = \frac{3}{7}[/tex]
Multiply:
[tex]\displaystyle \cos \left(90 ^\circ - x\right) = \frac{3}{7} \cos x[/tex]
Find cosine. Recall that tangent is the ratio of the opposite side to the adjacent side. Therefore, the opposite side is 3 and the adjacent side is 7.
Thus, by the Pythagorean Theorem, the hypotenuse will be:
[tex]\displaystyle h = \sqrt{3^2 + 7^2} = \sqrt{58}[/tex]
Cosine is the ratio of the adjacent side to the hypotenuse. Therefore:
[tex]\displaystyle \cos x = \frac{7}{\sqrt{58}}[/tex]
Thus:
[tex]\displaystyle \cos \left(90 ^\circ - x\right) = \frac{3}{7} \left(\frac{3}{\sqrt{58}}\right)[/tex]
Use a calculator. Hence:
[tex]\cos \left(90 ^\circ - x\right) \approx 0.1688[/tex]
