Alan Smith

2021-12-30

How do I solve this?

$\mathrm{cos}3x={\mathrm{cos}}^{2}x-3{\mathrm{sin}}^{2}x$

Karen Robbins

Beginner2021-12-31Added 49 answers

If you write $\mathrm{cos}\left(3x\right)=\mathrm{cos}(x+2x)$ , you can then apply the identity for the cosine of a sum. After that you can apply the identities that reduce $\mathrm{cos}\left(2x\right)\text{}{\textstyle \phantom{\rule{1em}{0ex}}}\text{and}{\textstyle \phantom{\rule{1em}{0ex}}}\text{}\mathrm{sin}\left(2x\right)$ to functions of cosx and sinx. You'll end up with an expression in which all sines are squared, so you can apply the identity ${\mathrm{sin}}^{2}x=1-{\mathrm{cos}}^{2}x$ . You're left with no trigonometric expressions except $\mathrm{cos}x$ . Then the substitution $u=\mathrm{cos}x$ reduces it to an algebraic equation to be solved for u.

You shouldn't wait until you know how to solve it before you start working on it. If you start with$\mathrm{cos}(x+2x)$ and apply the identity for the cosine of a sum, you can just see where that takes you. That's how I did this.

You shouldn't wait until you know how to solve it before you start working on it. If you start with

aquariump9

Beginner2022-01-01Added 40 answers

hence by setting

so

nick1337

Expert2022-01-08Added 777 answers

Using

Find an equation of the plane. The plane through the points (2, 1, 2), (3, −8, 6), and (−2, −3, 1), help please

A consumer in a grocery store pushes a cart with a force of 35 N directed at an angle of $25}^{\circ$ below the horizontal. The force is just enough to overcome various frictional forces, so the cart moves at a steady pace. Find the work done by the shopper as she moves down a $50.0-m$ length aisle.

??What is the derivative of $\mathrm{arcsin}\left[{x}^{\frac{1}{2}}\right]$?

What is the derivative of $y=\mathrm{arcsin}\left(\frac{3x}{4}\right)$?

Determine if the graph is symmetric about the $x$-axis, the $y$-axis, or the origin.$r=4\mathrm{cos}3\theta $.

How to differentiate $1+{\mathrm{cos}}^{2}\left(x\right)$?

What is the domain and range of $\left|\mathrm{cos}x\right|$?

How to find the value of $\mathrm{csc}74$?

How to evaluate $\mathrm{sec}\left(\pi \right)$?

Using suitable identity solve (0.99)raised to the power 2.

How to find the derivative of $y=\mathrm{tan}\left(3x\right)$?

Find the point (x,y) on the unit circle that corresponds to the real number t=pi/4

How to differentiate ${\mathrm{sin}}^{3}x$?

A,B,C are three angles of triangle. If A -B=15, B-C=30. Find A , B, C.

Find the value of $\mathrm{sin}{270}^{\circ}$.