Calculating sin and cos functions

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Mohsin Shah
Mohsin Shah on 29 May 2011
Commented: Steven Lord on 29 Jun 2022
Hello, i calculated the value of sin(45) in Matlab, the result was sin(45)=0.8509 and for cosin i got cos(45)= 0.5253. From general mathematics we know that sin(45)=cos(45) then why Matlab is giving different results??

Accepted Answer

Paulo Silva
Paulo Silva on 29 May 2011
Those functions work in radians not degrees, try this
cosd(45)
sind(45)
  3 Comments
Walter Roberson
Walter Roberson on 18 Dec 2021
It is not clear to me why sin() of a scalar should result in a vector of length 4 ? Or why those particular values should be output ?

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More Answers (5)

bym
bym on 29 May 2011
sin() & cos() arguments are in radians. If you want degrees use
sind() cosd()
  3 Comments
Steven Lord
Steven Lord on 20 Apr 2020
If you're going to convert degrees to radians or vice versa, use the deg2rad or rad2deg functions moved from Mapping Toolbox to MATLAB in release R2015b rather than the "magic number" of pi/180.

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krishna sutradhar
krishna sutradhar on 23 Jun 2021
Edited: Walter Roberson on 18 Dec 2021
sin(2250 ) + cot(300 ) + tan-1 (1/2) + 10e-10 + 9x10-2 + (log1010)3 + (loge10)5
  2 Comments
Nishith Sarkar
Nishith Sarkar on 29 Jun 2022
Edited: Nishith Sarkar on 29 Jun 2022
Question: sin(225) + cot(30) + tan-1(1/2) + 10e-10 + 9x10-2 + (log1010)3 + (loge10)5
>> ns1=sind(225)
ns1 =
-0.7071
>> ns2=cotd(30)
ns2 =
1.7321
>> ns3=atand(1/2)
ns3 =
26.5651
>> ns4=10e-10
ns4 =
1.0000e-09
>> ns5=9*10^-2
ns5 =
0.0900
>> ns6=log10(10)^3
ns6 =
1
>> ns7=log(10)^5
ns7 =
64.7260
>> Nishith=ns1+ns2+ns3+ns4+ns5+ns6+ns7
Nishith =
93.4059

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Vishali Bansal
Vishali Bansal on 3 Oct 2021
>> cos^-1(0.23)

Adedotun Taiwo
Adedotun Taiwo on 14 Feb 2022
Cos(45)
  1 Comment
Walter Roberson
Walter Roberson on 14 Feb 2022
MATLAB is case sensitive. That would not work.
Cos(45)
Unrecognized function or variable 'Cos'.
Paulo correctly answered a decade ago that if you are using degrees, use sind() and cosd()

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Nishith Sarkar
Nishith Sarkar on 29 Jun 2022
Edited: Nishith Sarkar on 29 Jun 2022
Answer please::
x=3cos50π+10sin300π-cos100π
  2 Comments
Steven Lord
Steven Lord on 29 Jun 2022
You don't need to use Symbolic Math Toolbox here. Use the sinpi and cospi functions instead.
x = (0:8).'/2;
s = sinpi(x);
c = cospi(x);
result = table(x, s, c)
result = 9×3 table
x s c ___ __ __ 0 0 1 0.5 1 0 1 0 -1 1.5 -1 0 2 0 1 2.5 1 0 3 0 -1 3.5 -1 0 4 0 1

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