Sin 2x vs 2 Sin x
功能是最重要的课程之一mathematical objects, which are extensively used in almost all subfields of mathematics. The sine function which is denoted asf(x) = sinxis a trigonometric function defined from the set of real numbers onto the interval [-1, 1] and is periodic with period 2ᴫ.
The basic definition of the sine of an acute angle is done using a right-angled triangle. The sine of the angle is equal to the ratio of the length of the side opposite to an angle to the length of the hypotenuse. This definition can be extended to all the angles using the identities sin (-x) = – sinxand sin (ᴫ +x) = – sinxand sin (2nᴫ +x) = sinx.
For the next two sections considerf(x) = sinxandg(x) = 2x.
What is Sin 2x?
Consider the composite functionf o ggiven byf o g(x) =f(g(x)) =f(2x) = sin 2x. This function is quite similar to sinxwith the domain as the set of real numbers and the range as the interval [-1, 1]. This function is periodic with the period ᴫ (as opposed to the period 2ᴫ of sinx). Sin 2xcan be expanded by the identity Sin 2x= 2 sinxcosxtoo.
What is 2 Sin x?
Consider the composite functiong o fgiven byg o f(x) =g(f(x)) =g(sinx) = 2 sinx. This is also a periodic function with the same period as sinx,but twice the amplitude of it since -1 ≤ sinx≤ 1 implies -2 ≤ 2 sinx≤ 2. Its domain is the set of real numbers and the range is the interval [-2, 2]
What is the difference between Sin 2x and 2 Sin x? • Sin 2x is defined from the set of real numbers onto the interval [-1, 1], whereas 2Sin x is defined from the set of real numbers onto the interval [-2, 2]. • Sin 2x is periodic with period ᴫ but 2 Sin x is periodic with period 2ᴫ. |
Blancasays
The sin of some angle is easy. Get a ladder of length one metre, lie it on the floor and tilt up the ladder by the angle. The height of the end is called the sine or abbreviated sin. For small angles 2 sin x is nearly the same as sin 2x only if you measure angles in radians. To get radians multiply your degrees by 2 pi /360. For larger angles it is silly to imagine they could be equal. For example twice the square of 3 is obviously not the square of twice 3. Why should anyone think they are?