Services & Resources / Wolfram Forums / MathGroup Archive
-----

MathGroup Archive 2010

[Date Index] [Thread Index] [Author Index]

Search the Archive

Re: Inverse trigonometrical functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg106890] Re: [mg106857] Inverse trigonometrical functions
  • From: Andrzej Kozlowski <akozlowski at gmail.com>
  • Date: Tue, 26 Jan 2010 06:35:01 -0500 (EST)
  • References: <201001251006.FAA09293@smc.vnet.net>

On 25 Jan 2010, at 11:06, Arnold wrote:

> How by means of Mathematica to transform =
ArcSin[x*Sqrt(1-y^2)-y*Sqrt(1-x^2)] in ArcSin[x]-ArcSin[y]?
>

Note that:

TrigExpand[Sin[ArcSin[x] - ArcSin[y]]]

x*Sqrt[1 - y^2] - Sqrt[1 - x^2]*y

That means that x*Sqrt[1 - y^2] - Sqrt[1 - x^2]*y == ArcSin[x*Sqrt[1 - y^2] - Sqrt[1 - x^2]*y] provided
Abs[ArcSin[x] - ArcSin[y]]<=Pi/2 (assuming both x and y are reals between -1 and 1).

To see some examples, let

eq = ArcSin[x*Sqrt[1 - y^2] - y*Sqrt[1 - x^2]] ==
  ArcSin[x] - ArcSin[y];

then

eq /. {x -> 1, y -> -1}

False

eq /. {x -> 1, y -> 0}

True


Andrzej Kozlowski



  • Prev by Date: Re: Redshift Calcs in Mathematica 7+
  • Next by Date: Re: Re: Re: looping
  • Previous by thread: Inverse trigonometrical functions
  • Next by thread: simple question for mathematica (corrected)