Calculating sin and cos functions

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??

Answer 1

[Paulo Silva]

Those functions work in radians not degrees, try this

cosd(45)
sind(45)

[Mohsin Shah]

thank u so much

[Abdullah Amin]

y=sin(-75) then y variable should carry value

+1 -1 +75 -75

[Walter Roberson]

@Abdullah Amin

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 ?

Answer 2

[bym]

sin() & cos() arguments are in radians. If you want degrees use

sind()  cosd()

[Mohsin Shah]

thank u so much

[Muhammed Çelik]

or, you can do like this sin(degree*pi/180)

[Steven Lord]

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.

Answer 3

[krishna sutradhar]

sin(2250 ) + cot(300 ) + tan-1 (1/2) + 10e-10 + 9x10-2 + (log1010)3 + (loge10)5

[Walter Roberson]

sind(2250) + cotd(300) + atand(1/2) + 10e-10 + 9*10^-2 + log10(10)^3 + log(10)^5

ans = 92.8037

[Nishith Sarkar]

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

Answer 4

[Vishali Bansal]

>> cos^-1(0.23)

[Walter Roberson]

acos(0.23)

ans = 1.3387

Answer 5

[Adedotun Taiwo]

Cos(45)

[Walter Roberson]

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()

Answer 6

[Nishith Sarkar]

Answer please::

x=3cos50π+10sin300π-cos100π

[Walter Roberson]

Pi = sym(pi);
x = 3*cos(50*Pi) + 10*sin(300*Pi) - cos(100*Pi)

x = 

2

[Steven Lord]

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