The Purplemath Forums

I am reviewing my calculus and I stumbled over this forum just today by googling for some help on rate-of-change of an angle type word problems. We worked together on another virtual venue some time back. I am really glad to see that you have created this forum and I will try to help when I can. Che...

This airplane is flying at 500 km/h in a straight direction at a constant 5000 m. \theta is the angle of elevation from a fixed point of observation. What is the rate of change of \theta when it is 30°? Required to answer in DMS/s and round to one decimal place. Solution: Drew the right triangle as ...

Eliz, Appreciate your attention to details. Hmm, let's see, "Low d high minus high d low, over the square of what's below") - tan(\theta)\,%20=\,%20\frac{h}{b} , And here's where I made my error - I swapped the "square of "what's below" with the square of what was ab...

:oops: Wow, I must have been in "la la land". So, further corrections \frac{d\theta}{dt}\,%20=\,\frac{-100}{3}\,*\,\frac{3}{4} \frac{d\theta}{dt}\,%20=\,-25\,\frac{radians}{hr} \frac{-25}{hr}\,*\,\frac{180}{\pi}\,*\frac{hr}{60\,min}\,*\,\frac{min}{60\,s} =\,approx\,-0.3978873577\,\frac{\,d...

A jet flying due north at 640 mi/hr passes over this town at noon. 15 minutes later another jet flying due west passes over the same town. The planes are flying at the same altitude. At what time will they be separating at 872 mi/hr? ( edited ) The answer is 1:15 p.m. I tried . I think I must be mis...

5. Give the slope-intercept form of the equation for the line on which these two points lie: (4, -2) and (3, 8) 5.1) We need to find the slope. m\,=\frac{y_2 - y_1}{x_2 - x_1} . Plug the y-coordinates and the x-coordinates into the formula. That would be either m\,=\frac{8\, -\, (-2)}{3\,-\...

A PIZZA PARLOR HAS A CHOICE OF 13 TOPPINGS FOR ITS PIZZAS. fROM THESE 13 TOPPINGS MANY DIFFERENT 2-TOPPINGS PIZZAS CAN BE ORDERD? aSSUME THAT THE ORDER IN WHICH TOPPINGS ARE LISTED DOES NOT MATTER. This is a simple problem in combinations. You want to select 2 toppings out of 13 available. So it's ...

Which of the following are functions? The last two problems, i.e., b & c, are multi part relations consider all parts when determining whether or not these relations are functions. Explain your reasoning for a, b, and c. Iam thinking for problem (a) that it is a FUNCTION because the value could...

Subject: Which of the following are functions? f=x+5, f=3 if x>2, Which of the following are functions? The last two problems, i.e., b & c, are multi part relations consider all parts when determining whether or not these relations are functions. Explain your reasoning for a, b, and c. Iam thin...

Eliz, Thanks for taking a look. I almost gave up on this, but I just couldn't. I decided to experiment by creating a similar problem in which the rates were known, the time was known, and the requirement was to find the rate at which the two jets were separating at a given time. I contrived it to wo...