The Cosine Rule

A triangular sail $DEF\,$ has side $D E = 8.4$ m and side $D F = 11.2$ m. The area of the sail is 35 m².

Calculate the perimeter of the sail $D E F$ .
Give your answer to 3 significant figures.

[5]

A triangular sail $DEF\,$ has side $D E = 8.4$ m and side $D F = 11.2$ m. The area of the sail is 35 m².

Calculate the perimeter of the sail $D E F$ .
Give your answer to 3 significant figures.

[5]

The Cosine Rule Questions