You can use the sum and difference identities which for cosine is cos(a+b)= cosacosb-sinasinb
You are given that 1 inch = 2.54 centimeters, so to convert 12.4 inches to centimeters, you would multiply 12.4 in by 2.54 cm.
The 2 lengths + 2 widths of the rectangle will equal 160 meters
So, for example, length = 50 m and width = 30m would fit the bill
2*50 + 2*30 = 160 m
$648 because the sales tax is 600*0.08=48
600+48=648
