Trigonometry in Excel

[Guest]

The formula below gives a result of 79.935 degrees using calculator
cos A = (b² + c²) - a² / 2bc
a=25.0 in A57
b=21.5407 in B57
c=17.0 in C57

This formula below has error which I cannot fix.
I have been trying for a while with no luck.
It could be that I'm trying to approch it the same way as a calculator.
In E57
=IF(OR(A57="",B57="",C57=""),0,DEGREES(ACOS(B57^+C57^)-A57^/2*B57*C57)))

Or in E57 =IF(COUNT(A57:C57)<3,0),0,DEGREES(ACOS(B57^+C57^)-A57^/2*B57*C57)))
My answer should be 79.935 degrees
Does someone have an answer for this puzzle?
Many thanks in advance.
Serge

 

[Dana DeLouis]

Hi. I think the use of ( ) are slightly off. See if this work:
I've used Range names. Note that "c" has to be "c_" in Excel.

=DEGREES(ACOS((b^2+c_^2-a^2) / (2*b*c_)))

Returns your solution of 79.935.

 

[Ron Rosenfeld]

The formula below gives a result of 79.935 degrees using calculator
cos A = (b² + c²) - a² / 2bc
a=25.0 in A57
b=21.5407 in B57
c=17.0 in C57

This formula below has error which I cannot fix.
I have been trying for a while with no luck.
It could be that I'm trying to approch it the same way as a calculator.
In E57
=IF(OR(A57="",B57="",C57=""),0,DEGREES(ACOS(B57^+C57^)-A57^/2*B57*C57)))

Or in E57 =IF(COUNT(A57:C57)<3,0),0,DEGREES(ACOS(B57^+C57^)-A57^/2*B57*C57)))
My answer should be 79.935 degrees
Does someone have an answer for this puzzle?
Many thanks in advance.
Serge

You just need to properly arrange your parentheses:

=IF(COUNT(A57:C57)=3,DEGREES(ACOS((B57^2+C57^2-A57^2)/(2*B57*C57))),0)

--ron

 

[Guest]

Hello Dana,
Thank you for your reply.
My formula looks as follows now:
=IF(OR(A57="",B57="",C57=""),0,DEGREES(ACOS((B57^2+C57^2-A57^2) /
(2*B57*C57))))
And it works well thank you very much.
I see that I missed the '2' next to the karet. I was not thinking.
Can you explain to me your version & the underscore next to the 'c'.
If you don't have time it's ok.
Anyway I'm very happy for your help.

Much thanks
Serge

 

[Guest]

Hello Ron,
I tried your formula and it works well also. I need to study this one.
Thank you for your input. I learn something different.
Serge

 

[Dana DeLouis]

Can you explain to me your version & the underscore next to the 'c'.

Hi. I was just using Range Names. I gave A57 the name "a"...etc. The
letter "c" is a little different in Excel. The letters "c" and "r" are not
valid names in Excel. However, the letter "c_" is valid.

I see that I missed the '2' next to the karat

I thought the following version is interesting as it avoids the power
symbol.
However, it turns out to be a longer equation. Darn!

=IF(COUNTBLANK(A57:C57)>0,0,
DEGREES(ACOS(1+SUMX2MY2(B57-C57,A57) / (2*B57*C57))))