Alan

Let v be the boats speed in still water.

Downstream speed = v + 8 km/hr 

Time to get to 56 km:  t = 56/(v + 8)

Upstream speed = v - 8 km/hr 

Time to get to 24 km:  t = 24/(v - 8)

The times are the same so:  56/(v + 8) = 24/(v - 8)

56(v - 8) = 24(v + 8)

32v = 80*8

v = 80*8/32 

v = 80/4

v = 20 km/ hr

Arrange them in numerical order.  The median is then the middle one.

how much is cos 1 is it 0 or 1

It depends on the units of the 1. 

cos(1degree) = 0.99.. as listed by Guest above.

cos(1 radian) = 0.54.. 

Area = 2pi*r*h.   where r is radius and h is height.

So: r = Area/(2pi*h)

r = 1106/(2pi*11) cm 

I'll leave you to crunch the numbers.

You are right! Exponentiation takes precedence over multiplication.  I must be half asleep!

16r^4

y = mx + b

Using (5, 52):   52 = m*5 + b

Using (13, 124):  124 = m*13 + b

You now have two equations in two unknowns (m and b) so you should be able to solve for these two, then you will be able to write the equation of the straight line through the points in the form y = mx + b.

Let n = sqrt{17 - sqrt{m}},  where n is an integer.

n^2 = 17 - sqrt{m}

sqrt{m} = 17 - n^2

m = (17 - n^2)^2

Now let n be 1, 2, 3 etc. until 17 - sqrt{m} is no longer positive.

(I see geno has beaten me to it)

.

Reading the question more carefully, I see I have misinterpreted the angles.  The angle between incident and reflection is 45 degrees not 90 degrees, so we need to use the cosine rule:

a^2 = 100^2 + 120^2 - 2*100*120*cos(45°)   where a is the distance  between pocket and initial strike.

so a = sqrt(100^2 + 120^2 - 2*100*120*cos(45°))

a = 86 cm (to the nearest cm).