Which of the following are identities? Check all that apply.
A. cos(x+y)+cos(x-y)=cos^2x-sin^2y
B. sin(x-pi)=-sinx
C. sin(x+y)-sin(x-y)=2cosx siny
D. cos(x+y)+cos(x-y)=2cosx cosy

Answers

Answer 1

Answer: B, C, D

Step-by-step explanation:

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Answer 2

       Since, tigonometric identities are equal on both the sides (left hand side and right hand side) of the equation, Options (B), (C), and (D) represent the dientities.

Identification of the tigonometric identites: Trigonometric identities are the equalities having two trigonometric expressions equal for all values of the variables on both the sides.To prove the expression as identity prove both the sides of the equation are equal.

Option A

cos(x + y) + cos(x - y) = cos²2x - sin²2y

Left hand side = cos(x + y) + cos(x - y)

                        = cosx.cosy - sinx. siny + cosx.cosy + sinx.siny

                        = 2(cosx.cosy)

But the left side of the equation is (cos²2x - sin²2y).

Hence both the sides are not equal and it's not an identity.

OPtion (B).

sin(x - π) = -sinx

Left hand side = sin(x - π)
                        = -sinx sin(x - π)

                        = sinx.cosπ - cosx.sinπ

                        = -sinx - 0  

                        = -sinx  [Right hand side]

Since, both the sides are equal, it's an identity.

Option (C).

sin(x + y) - sin(x - y) = 2cosx.siny

Left hand side = sin(x + y) - sin(x - y)

                        = sinx.cosy + cosx.siny - sinx.cosy + cosx.siny

                        = 2cosx.siny

                         = Right hand side

Since, both the sides are equal, it's an identity.

Option (D).

cos(x + y) + cos(x - y) = 2cosx.cosy

Left hand side = cos(x + y) + cos(x - y)

                        = cosx.cosy - sinx.siny + cosx.cosy + sinx.siny = 2cosx.cosy                        

                        = Right hand side

Since, both the sides of the equation are are equal.  It's an identity.

       Therefore, Option (B), (C), (D) are the correct options.

Learn more about the trigonometric identities here,

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Step-by-step explanation:

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The most appropriate graph is the (d) line graphs

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Answer:

Step-by-step explanation:

The null and alternative hypothesis:

[tex]H_o \text{: Quality of management and reputation of company are independent}[/tex]

[tex]H_a \text{: Quality of management is not independent of the reputation of company }[/tex]

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Excellent           40               25        8        73

Good                 35               35        10       80

Fair                     25              10         12       47

Total                 100             70          30      200

The expected values  = (Row total/column total)/grand total)

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Good                  40             28             12

Fair                    23.5         16.45         7.05

O                E                    (O - E)²/E

40              36.5                0.3356

35              40                   0.6250

25              23.5                0.0957

25              25.55              0.0118

35              28                    1.7500

10               16.45                2.5290

8                 10.95               0.7947

10                12                    0.3333

12                 7.05                3.4755

                                            9.951

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[tex]df = (3 - 1 ) (3 - 1)[/tex]

[tex]df = (2)(2)[/tex]

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