Calculate cos0 to two decimal places

To calculate the cosine of angle θ we need the law of cosines:

c²=a²+b²-2*a*b*cosθ.

In our case a=7, b=8 and c=11. We solve for cosθ:

-2*a*b*cosθ=c²-a²-b², we divide by -2*a*b and get:

cosθ=(c²-a²-b²)/(-2*a*b)=-1/14=-0.07.

So the correct answer is B -0.07.

the law of definite proportions states samples of a compound will always contain the same proportion of elements by mass. in other words, a given compound will always contain the same elements in the same proportions by mass.the law of multiple proportions states when two elements combine with each other to form more than one compound, then the weights of one element that combine with a fixed weight of the other are in a ratio of small whole numbers.