I have to find an inverse sine. it would be sin-1(5/9) so how do i calculate this on my casio fx 260? Any help is appreciated

The sine and cosine function have a range between [-1, 1]. The domain of their inverse functions is [-1,1]. So 20/1 which is 20 is out of the domain of definition of the functions. No limitations for tangent and cotangent.

The inverse sine is defined only for numbers in the range [-1, +1].
The sine of a number is at most 1.0. There is no number whose sine is 1.5, which is what you're asking for.
The same applies to the cosine and inverse cosine.

Press the SHIFT key before the sin, cos, or tan keys. For example, to calculate the inverse sine of .5 (arcsin(0.5)), press SHIFT sin . 5 ) =

That is correct: there is an error in your request. The range of the sine function spans the closed interval [-1, 1]. Thus the domain of the inverse sine function (the arc-sine) is the interval [-1,1]. However you are asking the calculator to calculate outside of the domain (7/2=3.5). If you are using the hyperbolic sine sinh, that is another matter.

The trigonometric function [SIN],[COS] and [TAN] have inverse functions arc-sine, arc-cosine, and arc-tangent which are also implemented on scientific calculators. To access the inverse trigonometric functions you use the sequences [SHIFT][SIN], [SHIFT][COS] and [SHIFT][TAN]. The functions are marked on the body of the calculator as [SIN^-1], [COS^-1] and [TAN^-1].
When you use these functions, make sure that the angle unit is correctly set (as required by the problem you are solving) because the angle values returned are in the same unit as the one set.

The FX-115ES is somewhat different to other calculators you might know. The sequence of keys is more like writing up a calculation in a textbook, whereas for "normal" calculators operations are reversed in some places.
For example, with most calculators you would type 30 [sin] to calculate the sine function of 30 degrees, with the 115ES its [sin] 30 [=].

The 115ES has all the standard trigonometric functions:

• Standard functions (sin, cos, tan), type the [sin], [cos] or [tan] key followed by the argument.
• Inverse trigonometric (sin?¹, cos?¹, tan?¹), type [SHIFT][sin], [SHIFT][cos] or [SHIFT][tan] followed by the argument.
• Hyperbolic functions (sinh, cosh, tanh), type [HYP][sin], [HYP][cos], or [HYP][tan] followed by the argument.
• and finally inverse hyperbolic (sinh?¹, cosh?¹, tanh?¹), its [SHIFT][HYP][sin], [SHIFT][HYP][cos], or [SHIFT][HYP][tan] followed by the argument.

Arguments can be given as numbers with mantissa (2.718), as fractions (use the fraction key below [CALC]) or as degree, minute, second (30°12'45") using the [°'"] key for input. To switch between degrees (1 circle = 360°), radians (1 circle = 2?), or grad (1 circle = 400 gon), use [SHIFT][DRG>].

I depends on what you mean by INV.
On some Chinese (AUREX, Staples) calculators the second function key is marked as INV. If that is the key you have in mind, on Casios it is the [SHIFT] key. On Sharps it is marked as [2ndF]

If you have in mind the multiplicative inverse (the reciprocal) then your calculator has such a key and it is marked [x^-1]. It the key represented on the following table at the intersection of the 2nd column and the 9th line (RECIPROCAL)



If you are thinking about the inverse of functions, then know that each function shares the same physical key as its inverse. For example to access the arcsine (the function inverse of sine) you press the [SHIFT] key before [SIN]. On the calculator you will notice that near the [SIN] key and to its left there is [SIN^-1].

hello,
Use [SHIFT] [COS^-1], [SHIFT][SIN^-1] and [SHIFT][TAN^-1] the keys are the same as the direct function, but they are accessed via [SHIFT].
Be carefule with the angle units when handling trigonometric and inverse trigonometric functions
Hope it helps

Hello,
I have not yet seen a calculator that has a dedicated key for the cosecant , secant, nor cotangente functions, because they are directly connected with the sine, the cosine, and the tangente.

Cosecant (x) = 1/sin(x)
Secant (x) = 1/cos(x)
Cotangente(x) = 1/tan(x)

Do not confuse these functions with the inverse trigonometric functions, usually represented as
arccosine = arccos; on calculators cos^-1,
arcsine = arcsin ; on calculators sin^-1
arctangent= arctan ; on aclculators tan^-1

Hope it helps.