Find the exact value of cos (theta) for an angle (theta) with sin (theta) = 3/8 and with its terminal side in Quadrant I.

a. 5/8

b. - sqrt(55)/8

c. 8/3

d. sqrt(55)/8

Respuesta :

Answer:

[tex]\frac{\sqrt{55}}{8}[/tex]

Step-by-step explanation:

[tex]\sin(\theta)=\frac{3}{8}[/tex] is given.

We are also given that [tex]\theta[/tex]'s angle terminates in quadrant one which means all 6 trig ratios are positive there.

We will use Pythagorean Identity: [tex]\sin^2(\theta)+\cos^2(\theta)=1[/tex].

[tex](\frac{3}{8})^2+\cos^2(\theta)=1[/tex]

[tex]\frac{9}{64}+\cos^2(\theta)=1[/tex]

[tex]\cos^2(\theta)=1-\frac{9}{64}[/tex]

[tex]\cos^2(\theta)=\frac{64-9}{64}[/tex]

[tex]\cos^2(\theta)=\frac{55}{64}[/tex]

[tex]\cos(\theta)=\pm \sqrt{\frac{55}{64}}[/tex]

[tex]\cos(\theta)=\frac{\sqrt{55}}{8}[/tex].

Answer:

d

Step-by-step explanation:

Cos²theta = 1 - sin²theta

= 1 - (3/8)² = 55/64

Cos theta = sqrt(55)/8

Positive because Quadrant 1