Question

Estimate e^0.2 without a calculator.

Answer 1

e^x = 1 + x + x^2/2! + x^3/3! + x^4/4! + ...

where x is the power and

"!" means factorial such that n! means n*(n-1)*(n-2).......3.2.1

For e^-x, just replace x by -x,

e^-x = 1 - x + x^2/2! - x^3/3! + x^4/4! + ...

where x is the power and

"!" means factorial such that n! means n*(n-1)*(n-2).......3.2.1

eg: 4! = 4*3*2*1 =24

I hope this solves. You need to remember the expansion though.