Question

find the derivative of the trigonometric function….
f(theta)=(theta+1)cos theta

Answer 1

f(theta)=(theta+1)cos theta

Answer 2

is what I meant...

Answer 3

use product formula

Answer 4

that didn't help me understand how todo it…. I want to know step by step how to do it..

Answer 5

cosQ(d/dx(Q-1))+(Q-1)(d/dx(cosQ)

Answer 6

product rule
(f*g)' = f*g' + g*f '
f(x) = (x+1)cos x
f\(x) = (x+1)*-sin x + 1* cos x
= cos x - (1+x) sin x

Answer 7

for x read theta

Answer 8

for x read theta?

Answer 9

@cwrw238

Answer 10

yes i used x as the angle to replace theta thats all - as i'm too lazy to write theta...

so answer is cos(theta) - (1 + theta ) sin (theta)

Answer 11

ooohhhh ok ok !

Answer 12

thankyou for explaining it to me. I really do appreciate your help. @cwrw238

Answer 13

yw

Answer 14

would you use the product rule for y=x+cotx ?

Answer 15

no - this is a sum not a product
just differentiate term by term

the product rule is used where you have 2 functions multiplied together

eg x^2 sin x , x(1 + tan x) , x^3 ln x

Answer 16

ok I understand