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3 years ago

Find the value of cos 28°cos 62°– sin 28°sin 62°

Mathematics

1 answer:

Romashka [77]3 years ago

8 0

<h2>Answer:</h2>

cos 28°cos 62°– sin 28°sin 62° = 0

<h2>Step-by-step explanation:</h2>

From one of the trigonometric identities stated as follows;

cos(A+B) = cosAcosB - sinAsinB -----------------(i)

We can apply such identity to solve the given expression.

Given:

cos 28°cos 62°– sin 28°sin 62°

Comparing the given expression with the right hand side of equation (i), we see that;

A = 28°

B = 62°

∴ Substitute these values into equation (i) to have;

⇒ cos(28°+62°) = cos28°cos62° - sin28°sin62°

Solve the left hand side.

⇒ cos(90°) = cos28°cos62° - sin28°sin62°

⇒ 0 = cos28°cos62° - sin28°sin62° (since cos 90° = 0)

Therefore,

cos28°cos62° - sin28°sin62° = 0

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Use the augmented matrix method to solve the following system of equations. Your answers may be given as decimals or fractions.

Alexandra [31]

Answer:

$x\ =\ \dfrac{21}{5}$

$y\ =\ \dfrac{3}{5}$

z = 2

Step-by-step explanation:

Given equations are

x - 2y - z = 2

x + 3y - 2z = 4

-x + 2y + 3z = 2

from the given equations the augmented matrix can be written as

$\left[\begin{array}{ccc}1&-2&-1:2\\1&3&-2:4\\-1&2&3:2\end{array}\right]$

$R_2=>R_2-R_1\ and\ R_3=>R_3+R_1$

$=\ \left[\begin{array}{ccc}1&-2&-1:2\\0&5&-1:2\\0&0&2:4\end{array}\right]$

$R_2=>\dfrac{R_2}{5}$

$=\ \left[\begin{array}{ccc}1&-2&-1:2\\0&1&\dfrac{-1}{5}:\dfrac{2}{5}\\0&0&2:4\end{array}\right]$

$R_1=>R_1+2.R_2$

$=\ \left[\begin{array}{ccc}1&0&-1-\dfrac{2}{5}:2+\dfrac{4}{5}\\\\0&1&\dfrac{-1}{5}:\dfrac{2}{5}\\\\0&0&2:4\end{array}\right]$

$=\ \left[\begin{array}{ccc}1&0&\dfrac{-7}{5}:\dfrac{14}{5}\\\\0&1&\dfrac{-1}{5}:\dfrac{2}{5}\\\\0&0&2:4\end{array}\right]$

$R_3=>\dfrac{R_3}{2}$

$=\ \left[\begin{array}{ccc}1&0&\dfrac{-7}{5}:\dfrac{14}{5}\\\\0&1&\dfrac{-1}{5}:\dfrac{2}{5}\\\\0&0&1:2\end{array}\right]$

$R_1=>R_1+\dfrac{7}{5}R_3\ and\ R_2+\dfrac{1}{5}R_3$

$=\ \left[\begin{array}{ccc}1&0&0:\dfrac{14}{5}+\dfrac{7}{5}\\\\0&1&0:\dfrac{2}{5}+\dfrac{1}{5}\\\\0&0&1:2\end{array}\right]$

So, from the above augmented matrix, we can write

$x\ =\ \dfrac{21}{5}$

$y\ =\ \dfrac{3}{5}$

z = 2

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Answer:

$Hi!~I~am~beinggreat78,~and~I~will~help~you!$

Let's start by breaking down the problem.

This is how it should look. ↓

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What does that x mean? x is just a substituted value for the first 2 equations.

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Answer:

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Find the value of cos 28°​cos 62°​– sin 28°​sin 62°​

Find the value of cos 28°cos 62°– sin 28°sin 62°