The formula for the light bend would be n1*sin i= n2 * sin r
If you use "sin (90-x)= cos x" principle, you can change the sin in the equation into
n1*sin i= n2 * sin r
n1 * cos a= n2 * cos b
n2/n1= cos a/ cos b
Assuming the n constant is the ratio of the glass compared to water then the answer would be: cos a/ cos b
9.66
^ This is the tenths place.
Look at the number after it, if it's 5 or more we round up, if it's 4 or less we round down.
The number is 6, so we round up to 9.7.
You need to multiple 7 and 5 or you could just skip the answer
