Question on: JAMB Mathematics - 2014
If y = cos 3x, find \(\frac{\delta y}{\delta x}\)
A
\(\frac{1}{3} \sin 3x\)
B
\(-\frac{1}{3} \sin 3x\)
C
3 sin 3x
D
-3 sin 3x
Ask EduPadi AI for a detailed answer
Correct Option: D
y = cos 3x
Let u = 3x so that y = cos u
Now, \(\frac{\delta y}{\delta x} = 3\),
\(\frac{\delta y}{\delta x} = -sin u\)
By the chain rule,
\(\frac{\delta y}{\delta x} = \frac{\delta y}{\delta u} \times \frac{\delta u}{\delta x}\)
\(\frac{\delta y}{\delta x} = (-\sin u) (3)\)
\(\frac{\delta y}{\delta x} = -3 \sin u\)
\(\frac{\delta y}{\delta x} = -3 \sin 3x\)
Let u = 3x so that y = cos u
Now, \(\frac{\delta y}{\delta x} = 3\),
\(\frac{\delta y}{\delta x} = -sin u\)
By the chain rule,
\(\frac{\delta y}{\delta x} = \frac{\delta y}{\delta u} \times \frac{\delta u}{\delta x}\)
\(\frac{\delta y}{\delta x} = (-\sin u) (3)\)
\(\frac{\delta y}{\delta x} = -3 \sin u\)
\(\frac{\delta y}{\delta x} = -3 \sin 3x\)
Add your answer
Please share this, thanks!
No responses