EM-1361

Cosine rule

E Math · Secondary 3 · Medium · Cosine rule

In a triangle,

a=7

,

b=10

and the included angle

C=60^\circ

. Using the cosine rule, find the length of side

c

opposite angle

C

.

$8.89\text{ cm (correct to 3 s.f.)}$
$5.57\text{ cm}$
$13.3\text{ cm}$
$79\text{ cm}$

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