Euler formula real part (p55)

Average Error: 0.0 → 0.7

Time: 4.8s

Precision: 64

Math

\[\Re(\left(\frac{e^{x} + e^{-x}}{2} \cdot \cos y + \frac{e^{x} - e^{-x}}{2} \cdot \sin y i\right))\]

↓

\[\frac{{x}^{2} + \left(\frac{1}{12} \cdot {x}^{4} + 2\right)}{2} \cdot \cos y\]

Error

Bits error versus x

Bits error versus y

Derivation

1. Initial program 0.0

   \[\Re(\left(\frac{e^{x} + e^{-x}}{2} \cdot \cos y + \frac{e^{x} - e^{-x}}{2} \cdot \sin y i\right))\]

2. Simplified 0.0

   \[\leadsto \color{blue}{\frac{e^{x} + e^{-x}}{2} \cdot \cos y}\]

3. Taylor expanded around 0 0.7

   \[\leadsto \frac{\color{blue}{{x}^{2} + \left(\frac{1}{12} \cdot {x}^{4} + 2\right)}}{2} \cdot \cos y\]

4. Final simplification 0.7

   \[\leadsto \frac{{x}^{2} + \left(\frac{1}{12} \cdot {x}^{4} + 2\right)}{2} \cdot \cos y\]

Reproduce

herbie shell --seed 2020057 
(FPCore (x y)
  :name "Euler formula real part (p55)"
  :precision binary64
  (re (complex (* (/ (+ (exp x) (exp (- x))) 2) (cos y)) (* (/ (- (exp x) (exp (- x))) 2) (sin y)))))