Aim: Why do we even radian? complete revolution of a...
Transcript of Aim: Why do we even radian? complete revolution of a...
U8L2 Radians.notebook March 29, 2015
DoNow:
1) Does it make sense to use the number 360° for a complete revolution of a circle?
2) If you could reinvent mathematics and use a different number, what would it be? Why is yours better?
Aim: Why do we even radian?
U8L2 Radians.notebook March 29, 2015
If we ignore all manmade number systems for a complete circle, there will be one NATURAL way to define a complete circle.
U8L2 Radians.notebook March 29, 2015
We say a complete circle has 2π radian measure.
An angle is defined to be the arc intercepted by two rays sharing a common vertex at the center of a unit circle.
Basically, it is the circumference of the unit circle it intercepts
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U8L2 Radians.notebook March 29, 2015
360° 270° 180° 90°
Initial Side: Every angle has a side on the positive xaxis
Terminal side: The other object to determine an angle.
U8L2 Radians.notebook March 29, 2015
Converting between Degrees & Radians
2π radians = 360° π radians = 180°
radians degrees
radians degrees=
Ex1:
Ex2:
U8L2 Radians.notebook March 29, 2015
Shortcut: to convert from radians to degree, you can substitute 180° for π (if you see it in the numerator)
U8L2 Radians.notebook March 29, 2015
S = Θ r
Arc Length Angle in Radian
Radius
Simple Example: A clock whose 4" long minutehand went from 12 to 3. How much distance did the tip of the minutehand travel? Round to nearest tenth of an inch.
S
U8L2 Radians.notebook March 29, 2015
Arwa runs around the Unisphere in Flushing Meadows. During one of her practices, she ran on part of the circle. Her runningwatch calculated that her path in BLUE was 310feet. Arwa estimated that she ran about 125° around the circle. Calculate the radius of the Unisphere Monument.
U8L2 Radians.notebook March 29, 2015
NYC is located on 40.71° N of the equator, and Montreal is located directly north of NYC on 45.50° N of the equator. The distance between the two cities is 330 miles.
Calculate the radius of the Earth. (These are all real calculations)
U8L2 Radians.notebook March 29, 2015
Summary:
There are ____ radians in a complete circle.
The formula to solve for arc length (s) is _______
One thing we need to be careful is that ________________
To quickly convert into degrees, I can _______________ 5π6