Assume that an airplane is flying toward you at a constant height h = 1 mile and at a speed dxdt=−20 miles/hr. When the plane is 2 miles away, what is the rate of change of θ?

tan(θ)=h/x

A. dθ/dt=−6 degrees/second

B. dθ/dt=−4 degrees/second

C. dθ/dt=4 degrees/second

D. dθ/dt=6 degrees/second

explanation:

remove parenthesis:

=

apply rule

=

multiply fractions:

=

=

divide:

=

mordancy.

sample answer: you can determine whether each element of the domain is paired with exactly one element of the range. for example, if given a graph, you could use the vertical line test; if a vertical line intersects the graph more than once, then the relation that the graph represents is not a function.

let x and 400 - x be the two numbers.  

==> 0.80x + 0.85(400 - x) = 400 - 68 from the statement of the problem.  

< ==> 0.80x + 0.85(400 - x) = 400 - 68  

==> 340 - 0.05x = 332  

< ==> -0.05x = -8 ==> x = 160, the first number ==> 400 - x = 240, the second number.