# Help

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## 1. Selection a formula from the base

Necessary formula can be selected by two ways:

 Select from the catalog Find by keywords 1. Press the key "Catalog of formulas". At opened window click required point of menu. Before you can make quick search by headings (if you begin to type any letter, system will reduce the menu according to your request; e. g. inquiry "riang" will choose all headings, concerned with the triangle). 1. Type keywords to input field (at top of the page). You can require any part of word, but should have in view that system seek exact set of symbols (without taking morphology into consideration). For example, to find the formula "Pythagorean theorem", you can type: "Pythagorean", "Pythagor", "agor" and the like. Capital and small letters are not different.  2. The list of formulas under required heading will be appear. Usually there are figures with symbols before formulas. Click on necessary formula to select. 2. Press key "Go" and the list of search result will be appear. Choose necessary formula and click it to select.

Notice! Each formula has own unique address (URL), so you can add necessary formulas (or headings) to favorite bookmarks to further quick access.

## 2. Calculation a formula from the base

Type all variables' values except one (sought quantity). Decimal fraction can contain both point and comma (5.8 and 5,8 are equivalent). Common fractions, including forms with pi (3pi/4, 3*pi/4, pi/4, 3pi, 3*pi), can be used as variables' values also. In case of need choose units of variables (default - by SI). You can select necessary unit of each variable of the formula. Press key "Calculate" and result will appear under the formula.

Angle and time variables can be given and determined in accustomed form.
For angle variables: input value to a field in format degrees:minutes:seconds (the unit does not matter at all). For example, notation 120:15:28 means 120° 15' 28''.
For time variables: input value to a field in format hours:minutes:seconds (the unit does not matter at all). For example, notation 14:18:34 means 14 h 18 min 34 s.
If decision variable is angle or time one, the result will be given in usual forms (decimal and exponential), but moreover if you move mouse over this result, you can see decision in form dd° mm' ss'' or hours:minutes:seconds. This auxiliary result is not exact (rounded to whole seconds).

If calculation was successful, you could see the result in 4 forms:

 full form (without rounding) in decimal notation 58.385872856 (m2) truncated form (rounding to 3 symbols max.) in decimal notation 58.386 (m2) full form (without rounding) in exponential notation 5.8385872856 E1 (m2) truncated form (rounding to 3 symbols max.) in exponential notation 5.839 E1 (m2)

Remaining at the page you can type new values of variables and repeat calculation.

If calculation was failed, there were corresponding messages under the formula:

• "These variables have incorrect values:" and then a list of variables. This implies that value input fields of those variables contain not a number (e. g., hypotenuse's length = 1�8).
• "Values of these variables are outside of the admitted region:" and then a list of variables. For example, hypotenuse's length < 0.
Besides, for the present the system operates with real numbers and do not with complex numbers, so, some operations result to error, e.g. extraction of the even degree root from minus number.
Make values more accurate and press key "Calculate" again.

We strive not to make error in formulas. However, it is necessary to get check solution manually at first use of the formula for perfect exception of wrong results. Please inform us in case of incorrect calculation.

Notice! Calculation results have nowhere saved and disappear since page content modification. Please record all results!

## 3. Calculation of own formula

You can calculate both exist formula from the base and own arbitrary formula. Input field is on top-right part of the page. One should observe the rules of syntax when inputting a formula:
1. Variable' name can contain Latin letters and numbers only and begin from a letter only, for example, a, D, t0, ro, time12.
2. Use of functions (sin, cos...) and "pi" as value name is impossible.
3. Values' names are register-dependent, i. e. T1 � t1 � two different variables.
4. Decimal fraction can contain both point and comma (5.8 and 5,8 are equivalent). Common fractions, including forms with pi (3pi/4, 3*pi/4, pi/4, 3pi, 3*pi), can be used as variables' values also.
5. The multiplication mark is obligatory ("5x" is wrong, "5*x" is correct).

Possible functions:

 function name function look required entry natural logarithm (ln)  decimal logarithm (lg) ln x ln(x) ln(x+y)2 ln(x+y)^2 ln2(x+y)3 (ln(x+y)^3)^2 the root of a number √(5x+3y)(t+2) sqrt(5*x+3*y)^(t+2) the degree of a number a(2x+5) a^(2*x+5) exponential function e-x8a exp((-x)^(8*a)) sine sin x sin(x) cosine cos x cos(x) tangent tg x tg(x) cotangent ctg x ctg(x) arc sine arcsin x arcsin(x) arc cosine arccos x arccos(x) arc tangent arctg x arctg(x) arc cotangent arcctg x arcctg(x)

After input a formula to the field press key "Enter". Your formula and the list of auto-defined variables will appear at the page. You can get value of any single variable. Input values of all variables besides one (decision variable) and press "Calculate". If calculation was successful, you could see the result in 4 forms:

 full form (without rounding) in decimal notation 58.385872856 �2 truncated form (rounding to 3 symbols max.) in decimal notation 58.386 �2 full form (without rounding) in exponential notation 5.8385872856 E1 �2 truncated form (rounding to 3 symbols max.) in exponential notation 5.839 E1 �2

Remaining at the page you can type new values of variables and repeat calculation.

On failed calculation:

• If input field has incorrect value (not a number, e.g. "1a8"), it results to message "These variables have incorrect values:" and then a list of variables.
Besides, for the present the system operates with real numbers and do not with complex numbers, so, some operations result to error, e.g. extraction of the even degree root from minus number.
Make values more accurate and press key "Calculate" again.

Notice! Calculation results have nowhere saved and disappear since page content modification. Please record all results!  x

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