EM-3072

Cosine rule

E Math · Secondary 4 · Hard · Cosine rule

A triangle has sides of length 7 cm, 9 cm and 12 cm. Using the cosine rule, find the size of the angle opposite the side of length 12 cm, correct to 1 decimal place.

$96.4^\circ$
$83.6^\circ$
$63.6^\circ$
$46.4^\circ$

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