Q. 28

Question

In Exercises 21–30 in Section 8.2 you were asked to find the fourth Maclaurin polynomial P4(x) for the specified function. In Exercises 23–32 we ask you to give Lagrange’s form for the corresponding remainder, R4(x).

tan x 

Step-by-Step Solution

Verified
Answer

The remainder is 2sec6c+11sec4c tan2c+2sec2c tan4c15x5

1Step 1 : Given Information

Given equation : tan x

Theory used : For n>0, if |f(n+1)(c)|1 for every value of x, then using the Lagrange's form for the remainder, we have 

Rn(x)=f(n+1)(c)(n+1)!xn+1

So, the Lagrange's form for the remainder, R4(x) is 

R4(x)=f(5)(c)5!x5

2Step 2 : Calculating Lagrange’s form for the corresponding remainder

Calculating the derivatives :

1) f(1)(tan x)=sec2x

2) f(2)(tan x)=2sec2x tanx

3) f(3)(tan x)=2(sec4x+2sec2x tanx)

4) f(4)(tan x)=8(2sec6x+11sec4x tan2x+2sec2x tan4x)

So,

 R4(x)=8(2sec6c+11sec4c tan2c+2sec2c tan4c)5!x5          =2sec6c+11sec4c tan2c+2sec2c tan4c15x5