Question

help lease

Answer 1

do you know law of cosine?

Answer 2

no i dont :{

Answer 3

wait what

Answer 4

i'm trying to use the equation editor but failing...

Answer 5

the cosine rule when applied here is
2^2 = 3^2 + 4^2 - 2.3.4 cos theta

Answer 6

so you now need to solve for 2.3.4 cos theta

Answer 7

how

Answer 8

well use the rules of algebra

Answer 9

subtract 3^2 + 4^2 from both sides
then multiply through by -1

Answer 10

-24 ?

Answer 11

2^2 - 3^2 - 4^2 = 3^2 + 4^2 - 3^2 - 4^2 - 2.3.4 cos theta

so the 3^2 and 4^2 disappear from the right side

Answer 12

can you continue? No its not -24

Answer 13

oh wait is it 21

Answer 14

yea

Answer 15

-21 = - 2.3.4 cos theta
multiply both sides by -1
21 = 2.3.4 cos theta

Answer 16

k thanx

Answer 17

yw

Answer 18

the cosine rule is used if you know 2sides of a triangle and included angle or 3 sides and you require on of the angles. It can be applied to all triangles.