Substitute 2cos2(2x)-1 for cos(4x) into the equation cos(2x)-cos(4x)=1, and solve for cos(2x) .chwala said:Homework Statement
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Solve ##2sin3x.sinx=1##Homework Equations
The Attempt at a Solution
I used the identity ##( cos (A+B)= cos A cos B- sin A sin B),
(cos(A-B) = cos A cos B+sinA sinB)→
-(cos 4x-cos2x)= 2sin 3xsinx, (cos 2x-cos4x=1)##now i am stuck , is this correct_
using ##(cos 2x=2cos^2x-1)⇒(cos 4x=2cos^22x-1),→(2cos^22x-2cos^2x+1=0)##
is this correct, how do i move folks
ehild said:Substitute 2cos2(2x)-1 for cos(4x) into the equation cos(2x)-cos(4x)=1, and solve for cos(2x) .
ehild hahahahahahahha that is what i was looking for lol, greetings from Africa broehild said:Substitute 2cos2(2x)-1 for cos(4x) into the equation cos(2x)-cos(4x)=1, and solve for cos(2x) .
No.. I edited my previous post. I was talking about the approach in #3, but it looks like I misread your quadratic equation.chwala said:Are you suggesting i use sin3x≡3sinx−4sin3x
what do you mean by saying solve the quadratic using discriminant method...cnh1995 said:I'd suggest you use the triple angle formula for sine. It will get much simpler.
Edit: No I think your current approach is good. Solve the quadratic equation using the discriminant method.
grandma. :) You are welcome.chwala said:ehild hahahahahahahha that is what i was looking for lol, greetings from Africa bro
Well, I read the equation wrong and thought it was a quadratic equation in 2x while it actually contains 2x as well as x. The discriminant method is used to solve quadratic equations. You can see it here.chwala said:what do you mean by saying solve the quadratic using discriminant method...
The name is "quadratic formula" . Discriminant method is something different.cnh1995 said:Well, I read the equation wrong and thought it was a quadratic equation in 2x while it actually contains 2x as well as x. The discriminant method is used to solve quadratic equations.
Trigonometry is a branch of mathematics that deals with the study of triangles and their relationships between sides and angles.
The basic trigonometric functions are sine, cosine, and tangent. These functions are used to calculate the ratios between the sides of a right triangle.
To solve a trigonometry problem, you will need to identify the given information, determine which trigonometric function to use, and set up an equation using the given information. Then, use algebraic methods to solve for the unknown value.
Trigonometry is used in various fields such as engineering, physics, astronomy, and navigation. It is also used in everyday life for tasks such as determining the height of buildings or measuring distances.
The key principles of trigonometry include the Pythagorean theorem, the unit circle, and the trigonometric ratios. These principles help to establish relationships between the sides and angles of a triangle, which can be used to solve various trigonometry problems.