Eric Nicholas K's answer to Candice's Secondary 4 A Maths Singapore question.

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Eric Nicholas K
Eric Nicholas K's answer
5997 answers (Tutor Details)
An “or otherwise” approach using Pythagoras theorem in triangles ABD and ABC to find lengths AD and AC respectively, then the cosine rule in triangle ACD using 5 as the opposite length to the angle CAD of 45 degrees.