How to stop pi appearing as a text in the disp result?

I want to estimate the value of cos(pi/4) using the taylor series expansion around the point x=0, here is my code,

syms x
f= cos(x);
t6= taylor(f,x);
val=subs(t6,x,pi/4);
disp(val);

I expect the result as a floating number however the result is printed as : pi^4/6144 - pi^2/32 + 1

How can I overcome this?

Answer 1

[Dyuman Joshi]

Convert the symbolic value to floating point value -

format long
syms x
f = cos(x);
t6 = taylor(f,x);
val = double(subs(t6,x,pi/4));
disp(val)

   0.707429206709773

[Tuna Dikmen]

Thank you!

[Image Analyst]

That's not pi/4

val = pi / 4

val = 0.7854

[Dyuman Joshi]

@Image Analyst, OP is trying to estimate the value of cos(pi/4) not pi/4

cos(pi/4)

ans = 0.7071

[Image Analyst]

Sorry, you're right.

Answer 2

[Image Analyst]

I suggest you don't use symbolic terms at all. I suggest you just do it numerically with a for loop to sum some number of terms (like a thousand or so).

Answer 3

[Walter Roberson]

sympref('FloatingPointOutput', true);
syms x
f= cos(x);
t6= taylor(f,x);
val=subs(t6,x,pi/4);
disp(val);

0.7074

I do not recommend this approach: there is not much control over the number of digits output, and there are (in my opinion) too many places where you would want symbolic instead of floating point values.