Is -9 a rational or irrational number

Mathematics

1 answer:

daser333 [38]4 years ago

7 0

-9 is a rattional number because it is an integer and it can be squared.

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Need help on this as soon as possibke

miss Akunina [59]

LA = perimeter of base x height

Use Pythagorean theorem to find the base

4^2 + 6^2 = 52
Sq root of 52 is 7.2111...

4+6+7.2 = 17.2

17.2 x 8

137.6 is your answer

3 0

3 years ago

Use the sum and difference identities to find the exact values of the sine, cosine, and tangent of the angle. . 165 = 135 + 30

Serhud [2]

So lets get to the problem

165°= 135° +30° 

To make it easier I'm going to write the same thing like this 
165°= 90° + 45°+30° 

Sin165° 
= Sin ( 90° + 45°+30° ) 
= Cos( 45°+30° )..... (∵ Sin(90 + θ)=cosθ 
= Cos45°Cos30° - Sin45°Sin30° 

Cos165° 
= Cos ( 90° + 45°+30° ) 
= -Sin( 45°+30° )..... (∵Cos(90 + θ)=-Sinθ 
= Sin45°Cos30° + Cos45°Sin30° 

Tan165° 
= Tan ( 90° + 45°+30° ) 
= -Cot( 45°+30° )..... (∵Cot(90 + θ)=-Tanθ 
= -1/tan(45°+30°) 
= -[1-tan45°.Tan30°]/[tan45°+Tan30°] 

Substitute the above values with the following... These should be memorized 
Sin 30° = 1/2 
Cos 30° =[Sqrt(3)]/2 
Tan 30° = 1/[Sqrt(3)] 
Sin45°=Cos45°=1/[Sqrt(2)] 
Tan 45° = 1

4 0

4 years ago

Find the product of z1 and z2, where z1 = 7(cos 40° + i sin 40°) and z2 = 6(cos 145° + i sin 145°).

Oduvanchick [21]

For two complex numbers $z_1=re^{i\theta}=r(\cos\theta+i\sin\theta)$ and $z_2=se^{i\varphi}=s(\cos\varphi+i\sin\varphi)$ , the product is

$z_1z_2=rse^{i(\theta+\varphi)}=rs(\cos(\theta+\varphi)+i\sin(\theta+\varphi))$

That is, you multiply the moduli and add the arguments. You have $z_1=7e^{i40^\circ}$ and $z_2=6e^{i145^\circ}$ , so the product is

$z_1z_2=7\times6(\cos(40^\circ+145^\circ)+i\sin(40^\circ+145^\circ)=42(\cos185^\circ+i\sin185^\circ)=42e^{i185^\circ}$