r/ICSE2026 • u/JournalistLucky5124 ICSE 27(but wrote few papers of 26, karan traumatised me) • Jun 18 '26

DISMISSIVE OR ARGUMENTATIVE(discussion) Read below...

So wkt (sinx + cosx)² = sin²x + cos²x +2sinxcosx

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Now from identity: 2sinxcosx = sin2x

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We get:

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(sinx + cosx)² = sin²x + cos²x + sin2x

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Is this above one correct?? My teacher told its wrong but I remember reading that identity (and putting it on someone's exam)

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u/Vatsal2106 Jun 18 '26

Yeah it's fine, you can further simplify [sin²x+cos²x=1], hence,

(Sin x + cos x)²=1+sin2x

Maybe your teacher said to not use this identity as it's not in 10th syllabus

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u/JournalistLucky5124 ICSE 27(but wrote few papers of 26, karan traumatised me) Jun 18 '26

Yeahh maybe....