differentiate:what rule are you using?. aims: to learn results of trig differentials for cos x, sin...
DESCRIPTION
The derivative of sin xTRANSCRIPT
32 )1( xDifferentiate: What rule are you using?
Aims:• To learn results of trig differentials for cos x, sin x & tan x.• To be able to solve trig differentials that require the chain, product and quotient rules • To be able to reverse this process in order to integrate definite and indefinite expressions.
Trigonometry Lesson 5 (Differentiation & Integration)
The derivative of sin x
The derivative of sin xBy plotting the gradient function of y = sin x, we deduce that
dyy x xdx
If = sin then = cos
Functions of the form k sin f(x) can be differentiated using the chain rule.
Differentiate y = 2 sin 3x with respect to x.
So if y = 2 sin u where u = 3x
Using the chain rule:
In general using the chain rule, f f fIf = sin ( ) then = '( )cos ( )dyy x x x
dx
The derivative of cos x
The derivative of cos xBy plotting the gradient function of y = cos x, we deduce that
dyy x xdx
If = cos then = sin
Differentiate y = 3 cos (x3 + 4) with respect to x.
And similarly to the differentiation of sine, it can be shown using the chain rule,
f f fIf = cos ( ) then = '( )sin ( )dyy x x xdx
Differentiate these!11. sin4
2. cos(3 2)
x
x x
x
3
5
cos2 .4
sin .35(sinx) as same theiswhich
Try these on w/b’s1. sin 9
62. -cos7
x
x
4
5
3. 3sin
4. cos 6
x
x
4which is the same as (sinx)
The derivative of cos x
Find given that y = –x2 cos x.dydx
Let u = and v =
So
Using the product rule:
We can also now differentiate products and quotients which contain trig functions.
The derivative of tan xWe can differentiate y = tan x by writing it as
xyx
sin= cos
Then we apply the quotient rule with u = sin x and v = cos x :
dyy x xdx
2If = tan then = sec
dyy x xdx
= sin = cos
Derivatives & Integrals of trigonometric functionsThese are the differential we have seen:
dyy x xdx
= cos = sin
dyy x xdx
2= tan = sec
As integration is the reverse of differentiation it follows that:
cos sinx dx x c
sin cosx dx x c 2sec tanx dx x c
In A2 you will be only asked to integrate sine and cosine functions. It can also be shown using the reverse chain rule that when dealing with the cos and sin of linear functions:
1cos( + ) = sin( + ) +ax b dx ax b ca
1sin( + ) = cos( + )+ax b dx ax b ca
Trig Integration
Find 2sin 5x dx
Find 2
0(2 cos 4 )x dx
Complete wheel puzzle Exercise F pg 101 qu 1, 3, 5, 7. Exercise G pg 104 qu 1 c, f, e. 2 and 3. Then Exercise A pg 108 qu 2, 3b, 4b,d,f and 5b, c, f
(b)
Person A
Person B