Cosine rule

Solve the equation: a^2 = 49 +16 - 2 x 7 x 4 cos 60

• 27

• 37

• 47

• 57

When I calculate the length of a side doing the cosine rule, the last part I need to do is:

• take the inverse cosine

• press the equals button

• square my number

• take the square root

Calculate the length of the side where b = 12 and c = 16. The angle between b and c is 45 degrees. Give answer to 1dp

• 11.2

• 11

• 11.3

• 11.25

Calculate the size of a to the nearest whole number when b =17 and c = 9. The angle between b and c is 60 degrees.

• 16

• 15

• 18

• 17

When calculating the cosine of an angle, which one of these is incorrect?

• cos A = (b^2+c^2 -a^2) / 2bc

• cos B = (a^2+c^2 -b^2) / 2ac

• cos C = (b^2+a^2 -c^2) / 2ab

• cos A = (b^2+a^2 -c^2) / 2bc