Intervals¶
Answer type: interval
The student types interval notation — a domain, a range, or a solution set.
The minimum¶
Common Control:
$answer = "(2,5]"
Bracket type is significant: (2,5] and [2,5] are different answers, which is usually the point of the question.
Options¶
| Variable | Effect |
|---|---|
$answer |
the correct interval — required |
$reqdecimals |
accuracy of each endpoint: unless $abstolerance or $reltolerance is set, it sets an absolute tolerance of 0.5×10⁻ⁿ and adds an "accurate to n decimal places" tip; the number of decimals typed is not checked |
$answerformat |
comma-separated format flags, e.g. "nosoln" (adds a "No solution" choice beside the box; use $answer = "DNE" for that case); infinity (oo) needs no flag |
$ansprompt |
text before the input box; with "nosoln" it instead supplies the radio-button labels, separated by ; (interval solution;no solution) |
$answerboxsize |
width of the input box |
Unions and infinity¶
Unions are written with U. Infinity is oo and needs no $answerformat flag:
$answer = "(-oo,2) U (5,oo)"
An infinite endpoint always takes a round bracket.
Related types¶
calcinterval accepts expressions as endpoints (e.g. sqrt(2), 1/2; interval rejects them) and additionally reads $variables and $hidepreview. Both types share one scorer, so $abstolerance, $reltolerance (default 0.0015) and $requiretimes apply to interval as well.
Example¶
Common Control — setup:
$a = rand(2, 6)
Question Text:
<p>Give the domain of `f(x) = sqrt(x - $a)` in interval notation.</p>
Common Control, continued — answer and options:
$answer = "[$a,oo)"
$ansprompt = "Domain: "