Answer:
[tex] cos(R) = \frac{\sqrt{15}}{5} [/tex]
Step-by-step explanation:
To find the cosine of <R, apply the following trigonometric ratio formula:
[tex] cos(R) = \frac{adjacent}{hypotenuse} [/tex]
Adjacent = 3
Hypotenuse = √15
Plug in the values into the formula
[tex] cos(R) = \frac{3}{\sqrt{15}} [/tex]
Multiply the numerator and denominator by √15 to rationalize.
[tex] cos(R) = \frac{3 \times \sqrt{15}}{\sqrt{15} \times \sqrt{15}} [/tex]
[tex] cos(R) = \frac{3\sqrt{15}}{(\sqrt{15})^2} [/tex]
[tex] cos(R) = \frac{3\sqrt{15}}{15} [/tex]
[tex] cos(R) = \frac{\sqrt{15}}{5} [/tex]
