Using Cos/Sin I lost my instructions on my Texas Instrument Calculator (TI-30XA), and I would like the steps in figuring out how to use cos/sin.

Make sure you have the proper angle mode set. Press MODE and check the third line.

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].

I'm going to use sin(90°) as an example. You would hit the sin button, type in 90, then hit ). You must type in the close parenthesis or the calculator won't read it correctly. The answer should be 1.

Make sure you're in the proper angular mode. Enter the value and press the TAN key (or SIN, or COS, or whatever) and then press ENTER.

You can download a guidebook from
http://education.ti.com/educationportal/sites/US/productDetail/us_ti30xa.html?bid=6

You would press on the SIN key, "sin(" should come on the display, then enter the value, for example 3.5 or -1 so that the display shows

sin(3,5) or sin(-1) for example.

remember to close the sin with the ) on the end.
sin(-1) = -0.841470985

for function = (sin,cos,tan,sec,cosec,cotan)
arc(function) = function^-1, calculated in the first quadrant for simplicity(0-pi/2) (0-90deg), as all functions repeat circularly
just another method of notation

http://www.mathwords.com/t/tangent_inverse.htm

if the sides of a triangle are 15cm ,16cm, and 17 cm ,then the area of the triangle is what ?

Make sure you are set to degrees, radians, or grads, whichever angular measurement you are using.

The DRG key toggles through the three modes of input, and the display shows which you are in.

30 SIN will give the correct 0.5 answer if you are set to use DEG.

Set to RAD and since 30 degrees = (30)(pi)/180= 0.52234 rad, set to RAD and 0.52234 SIN also gives you the correct 0.5 result

if you want to square sin(3), press:

(
sin
3
)
)
^
2

here are the steps in changing it from radian to degrees
1. turn on your TI-83 plus
2. press the MODE button near the top of your calculator
3.go down to options and move the highlight from radian to degree, press enter and clear
you're good to go