Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

- Index
- » Exercises
- »
**Derivative**

Pages: **1**

**Zeeshan 01****Member**- Registered: 2016-07-22
- Posts: 746

F(x)=e^x * cos (x-a)

Want to exercise this type of question

Know simple derivation but want to get this answer that is

Derivative=re^x cos(x-a+thetha)

R=sqrt 2 thetha=pi/4

M.M.Zeeshan.K

Offline

**Bob****Administrator**- Registered: 2010-06-20
- Posts: 8,930

hi Zeeshan 01

There are two stages to this problem. I think you have done the first but I'll say anyway.

This is a product of two functions so use the product rule:

You can combine the trig functions into a single trig function using the compound angle formulas. You want a cosine so I'll use

To make the derivative look like the right hand side here:

Hope that helps,

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Sometimes I deliberately make mistakes, just to test you! …………….Bob

Offline

Pages: **1**

- Index
- » Exercises
- »
**Derivative**