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Prove by counter example, that the statement:
cosec x - sin x > 0 for all values in the interval 0< x < Pi
is false

2007-01-27 03:41:19 · 5 answers · asked by Emma C 4 in Science & Mathematics Mathematics

The wording of the question is confusing me!

Am I proving that it is false and doing that by giving a value which makes the equation equal below zero?

2007-01-27 03:42:19 · update #1

5 answers

For x = pi /2, sin x =1 and cosec x = 1,

so : for x = pi /2 where 0< pi/2< pi, cosec x - sin x = 0, which contradicts: cosec x - sin x> 0
So the statement:
cosec x - sin x > 0 for all values in the interval 0< x < Pi
is false

2007-01-27 03:52:25 · answer #1 · answered by Anonymous · 0 0

You've to prove that the statement is false, citing an example.

x = Pi/2 should do the trick in which case,

cosec x - sin x = 0

2007-01-27 03:45:12 · answer #2 · answered by Avi 2 · 2 0

Let x=¶/2
cosec x - sinx = 1/sinx - sinx
= 1/sin(¶/2) - sin(¶/2) = 1/1 -1 = 0
This is therefore a counter example (because 0 is not greater than 0)

2007-01-27 20:28:22 · answer #3 · answered by Como 7 · 0 0

consider left hand side

cosecx=1/sinx
cosecx-sinx=1/sinx-sinx
=1-square of sinx
=square of cosx
when x =0.5,we get the square of cosx =0.9999>0 .
when x=1 the answer becomes 0.9997>0
when x=2 the answer becomes 0.9988.
therefore cosecx-sinx>0 for all values in the interval 0 note the values 0.5,1and 2 are all in the required range 0

2007-01-27 05:42:14 · answer #4 · answered by journey692002 1 · 0 1

it means find a number between 0 and pi where sin(x) is greater than csc(x). Easiest way would be grab a graphing calculator and graph them both to find a point where that happens.

2007-01-27 03:45:58 · answer #5 · answered by Anonymous · 0 1

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