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Natalija [7]
3 years ago
13

By writing sin 3x = sin(2x+x), show that sin 3x = 3 sin x - 4 sin^3 x.

Mathematics
1 answer:
Ksju [112]3 years ago
8 0

Given the trigonometry expression:

sin 3x = sin(2x+x),

In trigonometry identity;

Sin(A+B) = sinAcosB + cosAsinB

The expression above will then become;

sin(2x+x) =sin2xcosx+cos2xsinx\\sin(2x+x) =2sinxcosxcosx + (1-2sin^2x)sinx\\sin(2x+x) =2sinxcos^2x + (1-2sin^2x)sinx\\

Recall that sin^2x + cos^x = 1, hence;

sin(2x+x) =2sinx(1-sin^2x)+ (1-2sin^2x)sinx\\Expand\\sin(2x+x) =2sinx-2sin^3x+ sinx-2sin^3x\\sin(2x+x) =2sinx + sinx-2sin^3x-2sin^3x\\sisn(2x+x) = 3sinx-4sin^3x

This shows that sin3x =3sinx-4sin^3x (Proved!)

Learn more here: brainly.com/question/7331447

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Tems11 [23]
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Aye Sir!
4 0
4 years ago
F(x)=2x^2-x-10 part a: what are the X intercepts of the graph of f(x)? Show your work
Genrish500 [490]
A. x intercepts are where the graph hits the x axis or where f(x)=0
0=2x^2-x-10
solve
hmm
we can use the ac method
multiply 2 and -10 to get -20
what 2 numbers muliply to get -20 and add to get -1 (the coefint of the x term)
-5 and 4
split the midd into that
0=2x^2+4x-5x-10
group
0=(2x^2+4x)+(-5x-10)
factor
0=2x(x+2)-5(x+2)
undistribute
0=(x+2)(2x-5)
set each to 0
0=x+2
0=-2

0=2x-5
5=2x
5/2=x

x intercepts are at x=-2 and 5/2 or the points (-2,0) and (5/2,0)


B. ok, so for f(x)=ax^2+bx+c
if a>0, then the parabola opens up and the vertex is a minimum
if a<0 then the parabola opens down and the vertex is a max

f(x)=2x^2-x-10
2>0
opoens up
vertex is minimum

ok, the vertex

the x value of  the vertex in f(x)=ax^2+bx+c= is -b/(2a)
the y value of the vertex is f(-b/(2a)) so
given
f(x)=2x^2-x-10
a=2
b=-1
-b/2a=-(-1)/(2*2)=1/4
f(1/4)=2(1/4)^2-(1/4)-10
f(1/4)=2(1/16)-1/4-10
f(1/4)=1/8-1/4-10
f(1/4)=1/8-2/8-80/8
f(1/4)=-81/8
so the vertex is (1/4,-81/8) or (0.25,-10.125)


C. graph the x intercepts and the vertex
the vertex is min and the graph goes through the x intercepts
4 0
3 years ago
two teams are playing in the finals for an adult soft leauge. Each team has 13 players and the ages of the team members are show
Andrew [12]

Answer: C.

Step-by-step explanation:

6 0
3 years ago
???????????i need help on this ASAP!!!!
ioda
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3 0
3 years ago
Read 2 more answers
What is the Greatest common factor for -8X²+ 24​
monitta

Answer:

8

Step-by-step explanation:

- 8 {x}^{2}  + 24 \\  = 8( -  {x}^{2}  + 3) \\

5 0
3 years ago
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