Edexcel Mathematics June 2023 · Paper 2 · Question 15 · ExamRizz

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June 2023 · Paper 2 · Question 15 · 3 marks

15. A student attempts to answer the following question: Given that x is an obtuse angle, use algebra to prove by contradiction that sin x – cos x  1 The student starts the proof with: Assume that sin x – cos x < 1 when x is an obtuse angle Þ(sin x – cos x)2 < 1 Þ... The start of the student’s proof is reprinted below. Complete the proof. (3) Assume that sin x – cos x < 1 when x is an obtuse angle Þ(sin x – cos x)2 < 1 47

Lesson: Proof by Deduction