sstrike's answer to Macdaddy's Secondary 3 A Maths Singapore question.

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sstrike
Sstrike's answer
5567 answers (A Helpful Person)
Arnold K H Tan
Arnold K H Tan
1 year ago
Made a careless mistake at your second last line... its 6 x sqrt2, not 3 x sqrt2...

The approach you used, is the best, if the student is in Sec 3 and has not yet learnt the cosine rule.