EM-3063

Cosine rule

E Math · Secondary 4 · Hard · Cosine rule

In triangle PQR,

PQ = 7\text{ cm}

,

PR = 10\text{ cm}

and

QR = 12\text{ cm}

. Find

\angle QPR

correct to 1 decimal place using the Cosine Rule.

$87.9^\circ$
$52.1^\circ$
$39.0^\circ$
$27.9^\circ$

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