Let
x--------> the speed of the girl in step
y--------> the speed of the escalator in step
d------> the distance between ground and floor.
we know that

when the girl is going up on escalator
----> equation 
when the girl is going down on escalator
-------> equation 
Adds equation
and equation 

--------> equation 
Time to climb (in step) with y=0 (escalator standing still)
-----> equation 
Substitute equation
in equation 

therefore
the answer is

The quick way to get the answer is just type "42 choose 11" into Google.
Or if you want to figure it out yourself, you have 42 choices for the first potential juror, 41 choices for the second potential juror, etc.
Now before you stop there, you only care about the combination of the 11 people chosen, not what order they are selected, so you need to divide by the ways to arrange 11 people.
Final expression:
C(42,11) = (42 * 41 * 40 * 39 * 38 * 37 * 36 * 35 * 34 * 33 * 32) / (11 * 10 * 9 * 8 * 7 * 6 * 5 * 4 * 3 * 2 * 1)
Answers:
4,280,561,376 ways
We are asked to prove tan(θ / 2) = sin θ / (1 + cos θ). In this case, tan θ is equal to sin θ / cos θ. we can apply this to the equality. sin θ is equal to square root of (1-cos θ)/2 while cos θ is equal to <span>square root of (1 + cos θ)/2.
Hence, when we replace cos </span><span>θ with </span>square root of (1-cos θ)/2, we can prove already.
Triangle DEF hope that helps
Answer:

Explanation:
Here, we want to use the factor theorem to check if the given linear expression is a factor of the binomial
Now, according to the factor theorem, a factor of a polynomial would leave no remainder when divided by it
Mathematically, it means when we substitute the factor value into the polynomial, it is expected that the remainder is zero is the substituted is a factor of the polynomial
We set x-2 to zero:

Now, we substitute 2 into the polynomial as follows:

There is a remainder of -28 and thus, the linear factor is not a factor of the binomial