Web results for: cos-3pi-5

### Inverse Cos 1 and -1 : Special cases of the Inverse of ...

Inverse Cosine of 1 and -1, explained with pictures of both the unit circle and the cosine graph

### Finding cos (pi / 5) - Math Help Forum

Thankyou very much! With your information, I managed to get this: Cos (pi / 5) = Cos((pi/2) - (3pi / 10)) Cos (pi / 5) = Cos(pi/2)Cos(3pi/10) + Sin(pi/2)Sin(3pi/10)

### Cos 3pi/5 - Math Help Forum

Cos 3pi/5 I don't understand the step where 2Sin^2(3pi/10) = 2((sqrt5+1)/4) Follow Math Help Forum on Facebook and Google+. December 12th 2012, 01:07 AM #2.

### sin(2pi/5)cos(3pi/5)+tan^2(3pi/5)cos^2(3pi/5)Use ...

ANSWER: Using the complementary angles properties and basic identities of trigonometry, the sum sin(2pi/5)*cos(3pi/5) + tan^2(3pi/5)*cos^2(3pi/5) = 1.

### Finding the exact value of cos^-1(cos[17pi/5])? | Yahoo ...

Now 0< 3pi/5< pi So arccos(cos[3pi/5]) = 3pi/5 by the above principle **arccosx is the inverse of cosx for 0<=x<=pi** Source(s): guyava99 · 8 years ago . 0

### Working with exact values of sin,cos and tan - Free Math Help

I would appreciate any help on understanding how to convert from radian measure to exact values please! Suppose I have; sin 1/3 Pi and I was asked to find the exact ...

### Without a calculator, how can you find the exact value of ...

Without a calculator, how can you find the exact value of cos(3pi/5)? Follow . 1 answer . Report Abuse. ... Find Exact Value Without Calculator?

### Find the exact value of cos(3pi/5). Hint: First show that ...

Best Answer:: 3pi/5 = pi-2pi/5 so sin (3pi/5) = sin(pi-2pi/5) = sin 2pi/5 cos 3pi/5 = - cos 2pi/5 and this link below helps you to find the ans

### How do you evaluate cos((3pi)/5)cos((4pi)/15)+sin((3pi)/5 ...

Use the standard trig. formula: cos( a - b ) = cos(a)*cos(b) + sin(a)*sin(b) cos( (3Pi)/5) cos( (4Pi)/15) + sin( (3Pi)/5) sin( (4Pi)/15) becomes

### cos pi/5 - cos 3pi/5 = 1/2 - Ask an Expert at able2know

You need to check your math problem. cos pi/5 - cos 3pi/5 does NOT equal 1/2. It needs to be cos pi/5 + cos 3pi/5. I'm not sure about that second part.

### sec pi/4 *sin 3pi/20+sin pi/10-cos pi/10= 0 , how? | Yahoo ...

... cos(3pi/5) - sin(pi/10)sin(9pi/10) - 2sin(3pi/5)cos(pi/10)? Best Answer: (2pi/5) + (3pi/5) = pi So cos of one is negative of cos of the other.

### Inverse Cosine and Inverse Sine - CliffsNotes Study Guides

The inverse sine function's development is similar to that of the cosine. The restriction that is placed on the domain values of the sine function is.

### OpenStudy

cos(-3pi/5) = cos(3pi/5) so, arccos(cos(3pi/5)) = 3pi/5. gabby13. one year ago; Best Response. You've already chosen the best response. 0. I know but shouldn't the ...

### OpenStudy

So $(re ^{i \theta})^{5}=30=r ^{5} e ^{i 5\theta}$Now, in my above drawing, 30 is only a real number so its 'angle'=0 $5\theta=0$ \[\theta=0 ,or2\pi1/5,or 2\pi2/5 ...

### x^5 + 1 = 0 ....? | Yahoo Answers

so x = cos pi/5 + isin pi/5 , cos 3pi/5 + i sin 3pi/5 , cos pi + i sin pi , .... These are the 5 roots of -1. Source(s): Nishit V · 8 years ago . 11. 1

### Help needed (cos pi/5 + cos 3pi/5 = 1/2)? - qfak.com

Help needed (cos pi/5 + cos 3pi/5 = 1/2)? It says: Prove that cos pi/5 + cos 3pi/5 is 1/2. How do I do that? cosA + cosB = 2cos[(A+B)/2]

### How can I work out exact values without a calculator? 10 ...

... how can you find the exact value of cos(3pi/5)? Best Answer: Greetings, 3pi/5 is not a standard angle, so if you have a lot of time on ...

### How do you use the sum and difference identities to find ...

How do you evaluate #cos((3pi)/5)cos((4pi)/15)+sin((3pi)/5)sin((4pi)/15)#? How do you apply the sum and difference formula to solve trigonometric equations? See more

### How can you solve [Cos(pi/5) * Cos(2pi/5) = ?]?

How can you solve [Cos(pi/5) * Cos(2pi/5) = ?] the answer is 1/4 but, how to get that?

### How do we derive the value of cos 18 degree to be sqrt5-1 ...

But cos 18 can only be done with an infinite series. As a check ... (sqrt5) +1)/4, find the exact value for cos(3pi/5)? Find exact value of sin 2 ...

### SOLUTION: Use a sum or difference formula to find the ...

SOLUTION: Use a sum or difference formula to find the exact value of the following: {{{ sin(3pi/5)cos(7pi/30)+cos(3pi/5)sin(7pi/30) }}}

### Radians and Trigonometry. - Bored of Studies

Find the value of: cos(2pi/5)cos(3pi/5) - sin(pi/10)sin(9pi/10) - 2sin(3pi/5)cos(pi/10) :angry: THANK YOU

### Introduction to MATLAB - University of Maryland, College Park

Introduction to MATLAB ® copyright © 2000-2005 by Paul Green and Jonathan Rosenberg Working with the Command Window. How MATLAB appears when it first launches ...