answersLogoWhite

0

There are two ways to solve for the double angle formulas in trigonometry. The first is to use the angle addition formulas for sine and cosine.

* sin(a + b) = sin(a)cos(b) + cos(a)sin(b) * cos(a + b) = cos(a)cos(b) - sin(a)sin(b) if a = b, then

* sin(2a) = sin(a)cos(a) + cos(a)sin(a) = 2sin(a)cos(a) * cos(2a) = cos2(a) - sin2(b) The cooler way to solve for the double angle formulas is to use Euler's identity. eix = cos(x) + i*sin(x). Yes, that is "i" as in imaginary number.

we we put 2x in for x, we get

* e2ix = cos(2x) + i*sin(2x) This is the same as

* (eix)2 = cos(2x) + i*sin(2x) We can substitute our original equation back in for eix.

* (cos(x) + i*sin(x))2 = cos(2x) + i*sin(2x) We can distribute the squared term.

* cos2(x) + i*sin(x)cos(x) + i*sin(x)cos(x) + (i*sin(x))2 = cos(2x) + i*sin(2x) And simplify. Because i is SQRT(-1), the i squared term becomes negative.

* cos2(x) + 2i*sin(x)cos(x) - sin2(x) = cos(2x) + i*sin(2x) * cos2(x) - sin2(x) + 2i*sin(x)cos(x) = cos(2x) + i*sin(2x) Now you can plainly see both formulas in the equation arranged quite nicely. I don't yet know how to get rid of the i, but I'm working on it.

User Avatar

Wiki User

16y ago

What else can I help you with?

Related Questions

How do you solve identities on trigonometry?

Unlike equations (or inequalities), identities are always true. It is, therefore, not possible to solve them to obtain values of the variable(s).


How do you solve the hypotenuse of triangle APC if angle P is a right angle?

By using trigonometry or using Pythagoras' theorem for a right angle triangle.


How do you solve for x in a angle in a double angle?

lol hahaha


When given all three side lengths of a triangle but none of the angle measures you can solve for all angle measures using .?

With trigonometry by using the cosine rule


When given all three side lengths of a triangle but none of the angle measures you can solve for all angle measures using?

With trigonometry by using the cosine rule


What are the identities in trigonometry?

In trigonometry, identities are mathematical expressions that are true for all values of the variables involved. Some common trigonometric identities include the Pythagorean identities, the reciprocal identities, the quotient identities, and the double angle identities. These identities are used to simplify trigonometric expressions and solve trigonometric equations.


How do you solve sin18?

You can solve for sin18 by making use of trigonometry.


How do you solve 9- 2 equations?

7


How do you solve these equations?

Tell me the equations first.


How do you solve trigonometry proves?

by calculating the angles


Does this web site solve equations?

There are people who use this web site that can and will solve equations.


How can you use a graph to solve systems of equations?

You can use a graph to solve systems of equations by plotting the two equations to see where they intersect