If your solution to stated problem does not match the given solution, you should self-critique per instructions at

   http://vhcc2.vhcc.edu/dsmith/geninfo/labrynth_created_fall_05/levl1_22/levl2_81/file3_259.htm

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Your solution, attempt at solution.  If you are unable to attempt a solution, give a phrase-by-phrase interpretation of the problem along with a statement of what you do or do not understand about it.  This response should be given, based on the work you did in completing the assignment, before you look at the given solution.

SOLUTIONS/COMMENTARY FOR QUERY 6

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  ****   Query   problem 6.5.10 exact value of sin^-1( -`sqrt(3)/2)

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Your solution:  

Confidence Assessment:

Given Solution: 

 ** The inverse sine is between -`pi/2 and `pi/2. We are looking for the angle between these limits whose sine is -`sqrt(3) / 2. 

Since at this point we know how to construct the unit circle with values of the x and y coordinates for all angles which are multiples of `pi/4 or `pi/6, we know that the angle 5 `pi / 6 gives us y coordinate -`sqrt(3) / 2.  This angle is coterminal with an angle of -`pi/3, so sin^-1(-`sqrt(3) / 2) = -`pi / 3. **

INCORRECT STUDENT SOLUTION

Using the unit circle we can find that sin(sqrt(3)/2) is pi/3. The negative sign in front of the equation will make the pi/3
negative giving us -pi/3 as the value.
 
INSTRUCTOR RESPONSE AND CORRECTION

The negative sign means that we are looking for a negative value of the y coordinate, in the unit-circle model. This doesn't automatically make the angle negative. It works out that way for the inverse sine function, but would not for the inverse cosine.

The correct relationship would be sin(-pi/3) = - sqrt((3) / 2).

It would be correct to say that sin^-1(pi/3) = sqrt(3) / 2, but not that sin(sqrt(3)/2) = pi / 3.

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 Query   problem 6.5.34 exact value of cos(sin^-1(-`sqrt(3) / 2 )?

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Your solution:

Confidence Assessment:

Given Solution:

** sin^-1(sqrt(3) / 2) is the angle whose sine is sqrt(3) / 2.

It is therefore defined by a triangle whose base angle is opposite a 'downward vertical' side of length sqrt(3) and hypotenuse of length 2.

This triangle has adjacent side sqrt ( c^2 - a^2 ) = sqrt( 2^2 - (sqrt(3))^2) = sqrt(4 - 3) = sqrt(1) = 1.

The cosine of the base angle is therefore

cos( sin^-1(-sqrt(3)/2)) = adjacent side / hypotenuse = 1 / 2. **

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  ****   Query   problem 6.5.88  cos(tan^-1(v)) = 1 / `sqrt(1+v^2) 

explain how you establish the given identity. 

Your solution:  

Confidence Assessment:

Given Solution: 

 ** tan(`theta) = v defines a right triangle with side v opposite the angle `theta and side 1 adjacent to `theta.  The hypotenuse would thus be `sqrt(1+v^2).

It follows that cos(`theta) = adjacent side / hypotenuse = 1 / `sqrt(1+v^2).

Thus cos(tan^-1(v)) = adjacent side / hypotenuse = 1 / `sqrt(1+v^2).**

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