The old manual used to come with instructions to find angle in degrees of a right triangle if you kanw what the 3 lengths are . used to know formula but forgot it

If you know a, b, or c, you can figure out angle A. The sin(A) = a/h. To figure out what A is, you would use the arcsin(A). Angle B is the complementary of A so B = 90- A.

For example if a = 4, b = 3 and c = 5.

Sin(A) = 4/5 = 0.8

Arcsin(0.8) = 53.13 degrees

B = 90 - 53.13 = 36.87 degrees

Hope this helps you.

Hi - welcome to Fixya.

You're refering to Trigonometry or 'Trig'. The basic formula is easily remembered as SOH-CAH-TOA:

SOH: Sine of an angle is Opposite over Hypotenuse **
CAH: Cosine of an angle is Adjacent over Hypotenuse **
TOA: Tangent of an angle is Opposite over Adjacent **

** See attached image below

I can't tell you which buttons to press on your calculator, but you can download a new manual from here:

http://www.retrevo.com/support/TI-TI-30Xa-Calculators-manual/id/421ci270/t/2/

The download page will open in a new Browser window. Scroll down a little and click on "Download the Manual". On the next page, scroll to the bottom and enter the 5-digit security code in the box then click "Download" now. You can then save the file to your PC and/or print it for future reference. You don't need to enter your email address to download the manual. If you can't open the manual you may also need to download the latest version of Adobe Reader:

http://get.adobe.com/reader/

If you have any trouble downloading the instruction manual or you have any further maths questions, please post back and I will be happy to assist you.

Regards,
BElectric.

There is an exhaustive exposition of these calculations on THIS PAGE