lesson
Correctness includes not finding the target
1 · Learn
Linear search inspects items in sequence. It should return or report a match according to a stated rule, such as the first matching index, and handle absence explicitly. Duplicate values make that rule important.
For [6,2,6,9], searching for 6 and returning the first match gives index 0. A different requirement, finding all matches, needs continuing the search and collecting indices 0 and 2.
2 · Worked example
I write the requirement before choosing when to stop. Stopping at the first 6 is correct for first-match search but incomplete for all-match search.
3 · Your turn
In [6,2,6,9], what indices match 6? What is the first match?
Check your answer
Indices 0 and 2; the first is 0.
4 · Apply your learning
Trace first-match and all-match algorithms on the same list and compare their stopping conditions.
Adult guidance and safety
Use an approved private interpreter, simulator or authoring tool with fictional data. Trace and predict before running. Never execute unknown downloaded code, inspect real credentials or use other people's private data. Working examples still need saved-project and assessment integration before release.
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Check a calculation · Year 5 onward
Use this only when your teacher or adult allows a calculator for the task. Show your thinking first. It does not replace mental or written arithmetic and does not mark your lesson answer.
Powers, roots and trigonometry · Year 7 onward
Use only when the task allows a calculator. Choose one operation at a time and record your working. Trigonometry here always uses degrees (DEG), not radians. Inverse sine, cosine and tangent return an angle, not a reciprocal. Keep exact fractions and π in answers when requested.
Approximate numerical results use up to 12 significant digits. Inverse sine returns −90° to 90°, inverse cosine 0° to 180°, and inverse tangent −90° to 90°; these are principal values, not every possible solution of a trigonometric equation.
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