







Why 1/2 in the area of a circular sector? 
20181026 

From Ariel: In the equation for area of a sector=1/2r^2theta why is it 1/2? Please explain conceptually not algebraically. Answered by Penny Nom. 





Angle measures 
20120321 

From jogiboy: how can i get the sine theta if the given is 3.14/3 Answered by Penny Nom. 





The rate of change of the area of a parallelogram 
20110405 

From Gevork: Let a parallelogram have sides of 8 and 12 and let vertex angle A be decreasing at a rate of 2degrees per minute. Find the rate of change of the area of the parallelogram when angle A equals 30 degrees. Answered by Penny Nom. 





Angular velocity 
20100317 

From Lindsay: Determine the angular velocity, in radians per second, of a 14inch car wheel, if the car is traveling at 60 miles per hour Answered by Harley Weston. 





Angular speed 
20090804 

From Mary: The engine of a sports car rotates at 5000 revolutions per minute (rpm). Calculate the angular speed of the engine in radians per second. Use 2 radians = 1 revolution. Answered by Penny Nom. 





limit sinx/x 
20090130 

From Jackie: how to evaluate limit sinx/x as x tends to zero if x is in degrees Answered by Stephen La Rocque and Harley Weston. 





Radians 
20080208 

From Brian: I'm teaching Precalculus right now and will be covering the formula to convert angular speed into linear speed. My question is about the units involved. Using v=rw, if r is mearsured in feet and w is measured in radians/second then v is measured in ft/sec. What happened to the units of radians? I can't find a good way to explain why they are not part of units for velocity. Do you have a good explanation?
Thanks, Answered by Stephen La Rocque. 





Radial motion 
20071113 

From abdulai: a circular saw with diameter 18.4cm rotates at 2400rpm. What is the angular speed of a point on the edge of the saw blade in radians per second? Answered by Penny Nom. 





Is there a practical use for radian measure? 
20071026 

From Paula: Is there a practical use for radian measure in any profession? Which professions might us radian as opposed to degree measure? Answered by Harley Weston. 





Angular speed 
20070805 

From Virginia: the engine of a sports car rotates at 5,000 revolutions per minute (rpm). calculate the angular speed of the engine in radians per second. use 2n radians = 1 revolution Answered by Stephen La Rocque. 





What angle does the tire turn in 60s? 
20070604 

From San: An automobile, travelling at 80km/h, is towing a trailer. The wheels of the trailer
are 40cm in diameter. Through what angle does the tire turn in 60second? Answered by Stephen La Rocque. 





Angular speed 
20070106 

From Robert: A rear wheel and tire on a John Deere 8520 farm tractor has a 39in. radius. Find the angle (in radians) through which a wheel rotates in 12 sec if the tractor is traveling at a speed of 22 mph. Answered by Penny Nom. 





Degrees and grads 
20060406 

From Nazanin: which angle if you add 15 to its degree we can find its measure by grad? Answered by Stephen La Rocque. 





Is 360 Really the correct value? 
20050815 

From Jack: Considering the circumference of a "Perfect Circle" with a Diameter of 1 meter would be something like 3.14 meters, why do we use the number 360 to represent the number of degrees within that circumference?
Would it not make more sense to express the degrees in reference to the relationship to the diameter as related to pi?
That is, let's just say our "Perfect Circle" has a circumference of 3.14 meters, therefore, what we now consider as due east would change from 90 Degrees to 78.5 Degrees. Answered by Penny Nom. 





Radians 
20030116 

From Erikson: I am a student in the 10th grade and attending advanced math at my high school. I was assign to do a report about the unit circle and the radian. But there seems to be no information available about the history of the radian; who first found out about them, which civilizations used it if any. Well, hopefully you'll assist me in this troubling question. Thank you for your kind consideration. Answered by Penny Nom. 





3 radians subtends an arc of 27 meters 
20020522 

From Kyle: In circle O, a central angle of 3 radians intercepts an arc of 27 meters. Find the number of meters in the length of the radius. Answered by Penny Nom. 





Radian measure 
20010726 

From Amy: i have to find out what is meant by the radian measure of an angle and compare it to the measure of an angle in degrees. Answered by Harley Weston. 





PreCalculus 
20000809 

From Angela: Use absolute values to define the interval or pair of intervals on the real line.
<  ]    [ >
18 19 20 21 22 23 24 25 26
A car is moving at the rate of 50 miles per hour, and the diameter of its wheels is 2.5 feet. a) Find the number of revolutions per minute that the wheels are rotating. b) Find the angular speed of the wheels in radians per minute. Answered by Harley Weston. 





Arclength of a circle 
20000119 

From Holly: What is the formoula for finding the arc length of a central angle of a circle?? Answered by Harley Weston. 





The origin of angles 
19980224 

From Marc Poulin: I'm currently teaching angles to students in grade 10 and I've been asked what's the origin of the terms degrees, radians and gradians. I know that the radians come from the sexagesimal numerical system of the Babylonians but my kids wanted to know dates and persons who would have brought these terms first. Answered by Harley Weston. 





Why is a circle divided into 360 degrees? 
19960930 

From Kurtis Kredo: I was recently wondering why a circle has been divided in to 360 degrees. When I asked my physics teacher he could not think of an answer. His guess is that it probably has to do with people long ago using the base 6 number system. I have a small inkling that it has to do with easy conversion or usage with radians or grads. Answered by Chris Fisher. 





Un angle solide 
19980506 

From Giol: Qu'est ce qu'un angle solide ?? J'ai beau chercher dans mes documents, je ne trouve rien de bien convaincant sur le sujet si ce n'est une définition qui me semble bien vague et creuse ... En vous remerciant de votre attention ( puissiez vous illustrer votre réponse par un exemple, s.v.p...) Bonjour,
Answered by Chris Fisher. 

