Can I do sin cosign and tangent with the TI-15?

Sine Cosine and Tangent

Not directly. The calculator does not have the trig functions built in. You could do it the same way people did it before pocket calculators.

Not directly. The calculator does not have the trig functions built in. You could do it the same way people did it before pocket calculators, but you can't do it just be pushing one or two keys on this calculator.

To get the tangent of an angle, press "tan", enter the angle, and press "=".
See the example for sin on page E-10 of this manual: http://support.casio.com/pdf/004/fx-82ES_etc_E.pdf, replacing the "sin" with "tan".

There are several ways of doing this.

Opposite 12 and hypotenuse 13, so the sine of the angle is 12/13. Press 1 2 / 1 3 = 2nd [SIN^-1]

Adjacent 5 and hypotenuse 13, so the cosine of angle is 5/13. Press 5 / 1 3 = 2nd [COS^-1]

Adjacent 5 and opposite 12, so the tangent of the angle is 12/5. Press 1 2 / 5 = 2nd [TAN^-1].

The INV key that you may find on some scientific calculators has, on the TI 83/84/ Plus calculators, an equivalent key marked [2nd].

On the TI83/84 Plus, each trigonometric function has a second marking [SIN^-1], [COS^-1] or [TAN^-1]. To calculate the inverses of trigonometric functions ( arc sine, arc cosine, arc tangent) you press [2nd] followed by the relevant trigonometric function key For example, [2nd] [SIN] displays sin^-1( on the command line.

Unfortunately the hyperbolic functions and their inverses are only accessed through the CATALOG. You press [2nd][0] to open the CATALOG. Then you scroll down the CATALOG list to reach cosh(, cosh^-(, sinh(, sinh^-1(, tanh(, or tanh^-1(.
To speed the search in the catalog, you use the ALPHA keyboard: To reach cosh(, press[PRGM] and you scroll down from there.

Make sure your calculator is in degree mode.
It is probably in radian mode so it can't calculate the inverse sin.
To change this, go to Mode -> Deg.
Hope this helps, cheers!

Since you are familiar with sines, cosines, you know that their ranges (interval of values) varies from -1 to 1. The inverse functions of sine and cosine tkae their values in that very domain, [-1,1].
However you fed the arc sine function (sin^-1) a vlaue of (25/20.48) and that value is obviously larger outside the [-1,1] domain, hence the DOMAIN error message.

No such domain limitations exist for arc tangent (tan^-1) because the range of the tangent function spans the open interval ]negative infinity to positive infinity[.

By definition

1. cosecant of X =1/sin(X), must not be confused with arc sine [sin^-1]
   
2. secant of X =1/cos(X), must not be confused with arc cosine [cos^-1]
3. cotangent of X =1/tan(X), must not be confused with arc tangent [tan^-1]

Because of these simple relations, calculator makers do not implement them with specific key sequences.
On this calculator, you have two ways to calculate one of these functions. EX cosecant of 37 degrees

1. You enter 1 / [sin] 37 [ ) ] [ENTER] result is 1.661640141
2. You enter [sin] [ ) ] 37 [ENTER] followed by [X^-1] to take the reciprocal of the previous answer. The [X^-1] key is the one just below [MATH].

A word of caution: secant cosecant and cotangent must not be confused with the inverse trigonometric functions arcsin, arccos, arctan

Like the TI-85, it would be in the MATH menu.