Question

If sin t = 4/5 and t is in the first quadrant, find cos(2t)

Answer 1

ANSWER:

-7/25

STEP-BY-STEP EXPLANATION:

We can calculate the value of t, as follows:

$\begin{gathered} \sin t=\frac{4}{5} \\ t=\arcsin \mleft(\frac{4}{5}\mright) \\ t=53.13\text{\degree} \end{gathered}$

Now, we calculate the cosine of 2t, like this:

$\begin{gathered} \cos (2\cdot53.13) \\ \cos (106.26)=-0.28=-\frac{7}{25} \end{gathered}$