Respuesta :

sin(theta) = 4/5,[tex]cos^{2} (theta)=1-( \frac{4}{5})^{2} = 1 - \frac{16}{25} = \frac{9}{25} [/tex] We will switch it to formula: [tex]cos(2 theta)=cos^{2} (theta)-sin^{2} (theta)= \frac{9}{25} - \frac{16}{25}=- \frac{7}{25} [/tex]