Kaj je 4cos ^ 5thetasin ^ 5theta v smislu neeksponentnih trigonometričnih funkcij?

Kaj je 4cos ^ 5thetasin ^ 5theta v smislu neeksponentnih trigonometričnih funkcij?
Anonim

Odgovor:

# 1 / 8sin (2theta) (3-4cos (4theta) + cos (8theta)) #

Pojasnilo:

To vemo #sin (2x) = 2sin (x) cos (x) #. Uporabimo to formulo!

# 4cos ^ 5 (theta) sin ^ 5 (theta) = 4 (sin (theta) cos (theta)) ^ 5 = 4 (sin (2theta) / 2) ^ 5 = sin ^ 5 (2theta) / 8 #.

To tudi vemo # sin ^ 2 (theta) = (1-cos (2theta)) / 2 # in # cos ^ 2 (theta) = (1 + cos (2theta)) / 2 #.

Torej # sin ^ 5 (2theta) / 8 = sin (2theta) / 8 * ((1-cos (4theta)) / 2) ^ 2 = sin (2theta) / 8 * (1 - 2cos (4theta) + cos ^ 2 (4theta)) / 4 = sin (2theta) / 8 * ((1-2cos (4theta)) / 4 + (1 + cos (8theta)) / 8) = 1 / 8sin (2theta) (3-4cos (4theta)) + cos (8theta)) #