Page 444 - Excel for Scientists and Engineers: Numerical Methods

APPENDIX 4 EOUATIONS FOR CURVE FITTING 42 1

which relates vapor pressure of a pure substance to temperature, and the
Arrhenius equation

Ink=- -Ea +InA (A4- 1 8)
RT
which relates rate constant k of a reaction to temperature.

Trigonometric Functions. Excel's trigonometric functions require angles in
radians. For an angle 6' in degrees, use n6'/180.
The function represented by equation A4-19
y = a sin (bx + c) + d (A4- 19)
or its cosine equivalent produces a curve with the appearance of a "sine wave"
centered around the x-axis if d = 0, or offset from the x-axis if d # 0.
Functions of the form
y = sin ax + sin bx (A4-20)
and their cosine equivalents produce a "beat frequency" curve such as the one
shown in Figure A4-17.

Figure A4-18. "Beat fi-equency" curve.
The curve follows equation A4-21 with a = 1, b = 0.9.
Equation A4-21 combines the parameters of equations A4-19 and A4-20.

y =a sin (bx + c) + d sin (ex +A + g (A4-2 1)