JAMB - Mathematics (2025 - No. 32)
Find the derivatives of y = sin 4x
-4sin x
-4cos x
4sin4x
4cos4x
คำอธิบาย
Let 4x = u
y = sin u
\(\frac{\text{dy}}{\text{du}}\) = cos u
\(\frac{\text{du}}{\text{dx}}\) = 4
\(\frac{\text{dy}}{\text{dx}}\) = \(\frac{\text{dy}}{\text{du}}\) x \(\frac{\text{du}}{\text{dx}}\) = 4 x cos u
but u = 4x
Therefore, \(\frac{\text{dy}}{\text{dx}}\) = 4cos4x