tg t = a
sin t/cos t = a
sin t = a*cos t
sin^2 t = a^2 * cos^2 t
sin^4 t = (a^2 * cos^2 t)^2
sin^4 t = a^4 * cos^4 t
sin t cos t = acos t^2
sin t cos t = a(1-sin^2 t)
Therefore, sin t cos t = a(1 - a^2)
And sin^4 t = a^4 * (1 - a^2)^2
tg t = a
sin t/cos t = a
sin t = a*cos t
sin^2 t = a^2 * cos^2 t
sin^4 t = (a^2 * cos^2 t)^2
sin^4 t = a^4 * cos^4 t
sin t cos t = acos t^2
sin t cos t = a(1-sin^2 t)
Therefore, sin t cos t = a(1 - a^2)
And sin^4 t = a^4 * (1 - a^2)^2