Inverse Functions (1 Viewer)

3unitz

Member
Joined
Nov 18, 2006
Messages
161
Gender
Undisclosed
HSC
N/A
lacklustre said:
Sigh, another question:

sin-1(2sqrt2)/3 - tan-12

I get sin-1((2sqrt2)-2)/3sqrt5

The answer is tan-1(18-10sqrt2)/31

So can there be two answers to this question?
i.e. you can use sin(alpha - beta) or you could use tan(alpha - beta) right?
they are the same
 

lyounamu

Reborn
Joined
Oct 28, 2007
Messages
9,989
Gender
Male
HSC
N/A
lacklustre said:
Sigh, another question:

sin-1(2sqrt2)/3 - tan-12

I get sin-1((2sqrt2)-2)/3sqrt5

The answer is tan-1(18-10sqrt2)/31

So can there be two answers to this question?
i.e. you can use sin(alpha - beta) or you could use tan(alpha - beta) right?
The answer would be same for all even if you used different method (i.e. sine formula and tan formula).

If you check with your calculator, you answer is same as the answer (your answer is 7.0933054... and the answer is also 7.0933054...)

By the way, I got your answer as well.
 

lacklustre

Member
Joined
Jan 25, 2007
Messages
178
Gender
Undisclosed
HSC
2008
lyounamu said:
The answer would be same for all even if you used different method (i.e. sine formula and tan formula).

If you check with your calculator, you answer is same as the answer (your answer is 7.0933054... and the answer is also 7.0933054...)

By the way, I got your answer as well.
Ty for verifying that.

I'm really sorry to bother you guys but i have another question:

Evaluate: tan-1x + tan-11/x

I don't understand this q, when you simplify it, you get a zero in the denominator.
 

lyounamu

Reborn
Joined
Oct 28, 2007
Messages
9,989
Gender
Male
HSC
N/A
lacklustre said:
Ty for verifying that.

I'm really sorry to bother you guys but i have another question:

Evaluate: tan-1x + tan-11/x

I don't understand this q, when you simplify it, you get a zero in the denominator.
You get 0 as your denominator because if you add those together (whatever the value of x is), you get 90 degrees. tan 90 degrees is undefined as you know.

The answer being undefined basically means that x = all reals except 0.
 

lacklustre

Member
Joined
Jan 25, 2007
Messages
178
Gender
Undisclosed
HSC
2008
lyounamu said:
You get 0 as your denominator because if you add those together (whatever the value of x is), you get 90 degrees. tan 90 degrees is undefined as you know.

The answer being undefined basically means that x = all reals except 0.
Ok thanks that was a weird q for me. But i kinda get it.
 

lacklustre

Member
Joined
Jan 25, 2007
Messages
178
Gender
Undisclosed
HSC
2008
Can anyone assist me with this simple differentiation?:

d/dx sin(tan-1x)



I get (cos(tan-1x))/(1+x2)

The answer is different.
Cheers
 

3unitz

Member
Joined
Nov 18, 2006
Messages
161
Gender
Undisclosed
HSC
N/A
lacklustre said:
Can anyone assist me with this simple differentiation?:

d/dx sin(tan-1x)



I get (cos(tan-1x))/(1+x2)

The answer is different.
Cheers
its right, try to simplify cos(tan^-1x) to get the answer in the book.
 

lacklustre

Member
Joined
Jan 25, 2007
Messages
178
Gender
Undisclosed
HSC
2008
y = cos-1(1-x) <-- how do you sketch this? I thought i did it right, but when i checked on the computer the graph seems to be flipped upside down from a normal cos-1 graph.

Any help?
 

lyounamu

Reborn
Joined
Oct 28, 2007
Messages
9,989
Gender
Male
HSC
N/A
lacklustre said:
y = cos-1(1-x) <-- how do you sketch this? I thought i did it right, but when i checked on the computer the graph seems to be flipped upside down from a normal cos-1 graph.

Any help?
y = cos^-1(1-x)
cos y = 1-x
0 <_ y <_ pi

-1 <_ 1-x <_ 1
-2 <_ -x <_ 0
2 >_ x >_0

They are the domains & range. Draw the diagram according to this.

The shape of it will be like cot graph.
 
Last edited:

lacklustre

Member
Joined
Jan 25, 2007
Messages
178
Gender
Undisclosed
HSC
2008
lyounamu said:
y = cos^-1(1-x)
cos y = 1-x
0 <_ y <_ pi

-1 <_ 1-x <_ 1
-2 <_ -x <_ 0
2 >_ x >_0

They are the domains & range. Draw the diagram according to this.
I did get the domain and range (same as yours) but I didn't know the graph would be upside down to a normal inverse cos curve.

This is how i pictured it:
 

lyounamu

Reborn
Joined
Oct 28, 2007
Messages
9,989
Gender
Male
HSC
N/A
lacklustre said:
I did get the domain and range (same as yours) but I didn't know the graph would be upside down to a normal inverse cos curve.

This is how i pictured it:
Yeah the shape is same for both inverse and non-inverse. Only difference is where the graph is situated. You just draw the graph according to the domain & range.
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top