Question

Ost< and cost is given. Use the Pythagorean identity sin2 t + cos2 t = 1 to find sin t.18) cos i =316I need help with #18

Answer 1

sin^2t + cos^2t = 1

sint = 1/4

(1/4)^2 + cos^2 t = 1

1/16 + cos^2 t = 1

cos^2 t = 1 - 1/16

cos^2 t = (16 - 1)/16

cos^2 t = 15/16

take root both side,

$\begin{gathered} cost=\sqrt[]{\frac{15}{16}} \\ \cos t=\frac{\sqrt[]{15}}{4} \end{gathered}$

so the answer is option D