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2 years ago

Show that √(1-cos A/1+cos A) =cosec A - cot A

Mathematics

1 answer:

Gennadij [26K]2 years ago

5 0

Hi there!

$\sqrt{\frac{1-cosA}{1+cosA}} =$

We can begin by multiplying by its conjugate:

$\sqrt{\frac{1-cosA}{1+cosA}} * \sqrt{\frac{1+cosA}{1+cosA}} = \\\\\sqrt{\frac{(1-cosA)(1 + cosA)}{(1+cosA)(1 + cosA)}} =$

Simplify using the identity:

$1 - cos^2A = sin^2A$

$\sqrt{\frac{(1-cos^2A)}{(1+cosA)^2}} =\\\\\sqrt{\frac{(sin^2A)}{(1+cosA)^2}} =$

Take the square root of the expression:

${\frac{sinA}{1+cosA} =$

Multiply again by the conjugate to get a SINGLE term in the denominator:

${\frac{sinA}{1+cosA} * {\frac{1-cosA}{1-cosA} =\\$

Simplify:

${\frac{sinA(1-cosA)}{1-cos^2A} =$

Use the above trig identity one more:

${\frac{sinA(1-cosA)}{sin^2A} =$

Cancel out sinA:

${\frac{(1-cosA)}{sinA} =$

Split the fraction into two:

${\frac{1}{sinA} - \frac{cosA}{sinA} =$

Recall:

$1/sinA = cscA\\\\cosA/sinA = cotA$

Simplify:

$\frac{1}{sinA} + \frac{cosA}{sinA} = \boxed{cscA - cotA}$

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Answer:

its A

Step-by-step explanation:

Because m > 6/7. and if you do the sloving it will be 2 or greater

Hope that helped

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2 years ago

If a,b,c and d are positive real numbers such that logab=8/9, logbc=-3/4, logcd=2, find the value of logd(abc)

Eva8 [605]

We can expand the logarithm of a product as a sum of logarithms:

$\log_dabc=\log_da+\log_db+\log_dc$

Then using the change of base formula, we can derive the relationship

$\log_xy=\dfrac{\ln y}{\ln x}=\dfrac1{\frac{\ln x}{\ln y}}=\dfrac1{\log_yx}$

This immediately tells us that

$\log_dc=\dfrac1{\log_cd}=\dfrac12$

Notice that none of $a,b,c,d$ can be equal to 1. This is because

$\log_1x=y\implies1^{\log_1x}=1^y\implies x=1$

for any choice of $y$ . This means we can safely do the following without worrying about division by 0.

$\log_db=\dfrac{\ln b}{\ln d}=\dfrac{\frac{\ln b}{\ln c}}{\frac{\ln d}{\ln c}}=\dfrac{\log_cb}{\log_cd}=\dfrac1{\log_bc\log_cd}$

so that

$\log_db=\dfrac1{-\frac34\cdot2}=-\dfrac23$

Similarly,

$\log_da=\dfrac{\ln a}{\ln d}=\dfrac{\frac{\ln a}{\ln b}}{\frac{\ln d}{\ln b}}=\dfrac{\log_ba}{\log_bd}=\dfrac{\log_db}{\log_ab}$

so that

$\log_da=\dfrac{-\frac23}{\frac89}=-\dfrac34$

So we end up with

$\log_dabc=-\dfrac34-\dfrac23+\dfrac12=-\dfrac{11}{12}$

###

Another way to do this:

$\log_ab=\dfrac89\implies a^{8/9}=b\implies a=b^{9/8}$

$\log_bc=-\dfrac34\implies b^{-3/4}=c\implies b=c^{-4/3}$

$\log_cd=2\implies c^2=d\implies\log_dc^2=1\implies\log_dc=\dfrac12$

Then

$abc=(c^{-4/3})^{9/8}c^{-4/3}c=c^{-11/6}$

So we have

$\log_dabc=\log_dc^{-11/6}=-\dfrac{11}6\log_dc=-\dfrac{11}6\cdot\dfrac12=-\dfrac{11}{12}$

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2 years ago

Charlie wants to buy new carpet for his living room floor the floor is in the shape of a rectangle its length is 15 feet and the

sdas [7]

Answer:

135 square ft.

Step-by-step explanation:

To solve this equation, you need to find the area of this rectangle. Area is always base x height, or in this case, length x width. Now you multply your length, 15', by your width, 9', to get your answer, 135 square feet. When you multiply two measurments of the same unit together, you get square (units), which simply means that you multiplied two of the same unit of measurment together.

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2 years ago

A bolt falls off an airplane at an altitude of 500 m. How long will it take the bolt to reach

Rudik [331]

Answer:

t = sqrt(500/4.9) =~ 10.1 seconds/ Answer: 10.1015 seconds (this is approximate)

Step-by-step explanation:

Use 4.9t^2 + v0t = s

a) A bolt falls off an airplane at an altitude of 500 m. Approximately how long does it take the bolt to reach the ground?

s = 4.9t^2 + v0t = 500

4.9t^2 = 500

t = sqrt(500/4.9) =~ 10.1 seconds

Part A)

v = initial velocity = 0

s = 500 = vertical distance the object travels (from plane to ground)

Plug in the given values and solve for t

4.9t^2 + v*t = s

4.9t^2 + 0*t = 500

4.9t^2 + 0 = 500

4.9t^2 = 500

t^2 = 500/4.9

t^2 = 102.04081632653

t = sqrt(102.04081632653)

t = 10.101525445522

t = 10.1015

Answer: 10.1015 seconds (this is approximate)

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2 years ago

Bella earned the federal minimum wage in the year 2008. During that time, she worked 37.5 hours per week. How much money did she

Mariana [72]

Answer:

Belle's weekly earnings per week in 2008: $245.7

Step-by-step explanation:

The federal minimum wage in the year 2008 was: $6.55

She worked 37.5 hours per week.

She earn each week:

$weekly earnings = 6.55*37.5=245.7$

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2 years ago

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Show that √(1-cos A/1+cos A) =cosec A - cot A​

Show that √(1-cos A/1+cos A) =cosec A - cot A