1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
antoniya [11.8K]
3 years ago
13

Simplify the expression by using a double-angle formula. cos-39°– sin²39

Mathematics
1 answer:
AVprozaik [17]3 years ago
5 0

Answer:

cos 78⁰.

Step-by-step explanation:

Use cos 2A = cos^2 A - sin^2 A

so cos^2 39 - sin^2 39 = cos (2*39) = cos 78.

You might be interested in
Write the equation of the graph which is the reflection of y=−|x−1|−1 about the origin
Norma-Jean [14]

Answer:

f(x) = |x + 1| + 1

Step-by-step explanation:

A reflection over the y-axis followed by a reflection over x-axis is equivalent to a reflection about origin.

f(x) = -|x-1| -1

reflection over the x-axis:

-f(x) = (-1)*(-|x-1| -1) = |x-1| +1

reflection over the y-axis of the previous function:

-f(-x) = |-x-1| +1 = |x + 1| + 1

which is the reflection of f(x) about the origin

6 0
3 years ago
Find the positive value of x in the geometric sequence 7x-2,4x+4,3x
Goryan [66]
Hello,


Let's assume k the ratio.


 \left \{ {{3x=k*(4x+4)} \atop {4x+4=k*(7x-2)}} \right. \\\\
 \left \{ {{3x-4kx=4k} \atop {4x-7kx=-2k-4}} \right. \\\\
 \left \{ {{x(3-4k)=4k} \atop {x(4-7k)=-2k-4}} \right. \\\\
 \left \{ {{x=\dfrac{4k}{3-4k} \atop {x=\dfrac{-2k-4}{4-7k} \right. \\\\

\dfrac{4k}{3-4k}=\dfrac{-2k-4}{4-7k}\\\\

36k^2-6k-12=0\\
6k^2-k-2=0\\

\boxed{k= \dfrac{2}{3} \ or\ k= -\dfrac{1}{2}}\\\\

x=\dfrac{4*\dfrac{2}{3} }{3-4*\dfrac{2}{3} }=8\\
x=\dfrac{4*\dfrac{-1}{2} }{3-4*\dfrac{-1}{2} }=-\dfrac{2}{5}\\







\boxed{x= 8 \ or\ x= -\dfrac{2}{5}}\\\\





5 0
3 years ago
How do you solve right triangles in trigonometry
Ann [662]
In trigonometry, to solve right triangles, we use sine, cosine, and tangent (their definitions, and the laws of sine and cosine) to help us fill in the blanks. Do you need more information (I'm rusty on law of sines and law of cosines, but pretty fresh on definitions and identities).
4 0
3 years ago
one-fourth of an inch on a map represents 150 Mi the distance on the map from Springfield to Oakwood is 3 and 1/2 in how many mi
kogti [31]
I’m not sure You’d have to ask in a calculator
4 0
3 years ago
What property can I use for this question: 3x57
blondinia [14]

Answer:

<h2>====LEARN WITH REY====</h2>

What property can I use for this question: 3x57

In this property there is the property of the multiplication part

Step-by-step explanation:

If calculated, the result is

3 x 57 = 171

<h3>#Study with brainly </h3><h3># Learn with rey</h3>

<h3>Question code : 5.2.7</h3><h3>Course : Math</h3><h3>Theory : Splash</h3>
5 0
3 years ago
Other questions:
  • A circular well has a circumference of 7.85 yards. What us the diameter of the well
    12·2 answers
  • Select the expressions that are equivalent to 5(w+5)
    12·2 answers
  • Determine two pairs of polar coordinates for the point (3, 3) with 0° ≤ θ &lt; 360
    13·2 answers
  • My question is where is the nearest fraction store i need to know
    8·1 answer
  • Find the factor pairs of 46 and 76
    12·1 answer
  • Answer this Quickly Please 50 points !!!!!!!!!!!!!!!
    5·1 answer
  • Select the correct answer
    15·1 answer
  • List of all numbers less than 30 are divisible by 8?
    9·2 answers
  • Part A
    12·2 answers
  • Araba bought an electric Cooker for 540.00 ghanacedis at a discount of 10%.Find the actual price of the eletric cooker.
    15·2 answers
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!