sstrike's answer to Macdaddy's Secondary 3 A Maths Singapore question.
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.
The approach you used, is the best, if the student is in Sec 3 and has not yet learnt the cosine rule.