lesson
Smaller representations have trade-offs
1 · Learn
Lossless compression allows the exact original data to be reconstructed. Lossy compression discards selected information to reduce size, so decoding does not generally recreate the exact original. Choose according to what information must be preserved.
A smaller file is not automatically better if it removes necessary detail. Repeated lossy processing can introduce further changes, while compression ratios depend on the data and method.
2 · Worked example
Source code needs exact character recovery, while some media uses may tolerate carefully chosen losses. That does not make all lossy settings suitable for every image.
3 · Your turn
Which kind of compression guarantees exact reconstruction when correctly implemented: lossless or lossy?
Check your answer
Lossless.
4 · Apply your learning
Compare approved copies of an image at different settings and describe observable changes without claiming a universal best ratio.
Adult guidance and safety
Use an approved sandbox with invented data. Never ask for real passwords, personal records or access to another person's system. These text examples need executable projects and assessed evidence in two languages; reading code alone is not practical mastery.
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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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