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Evaluating an expression in terms of x:

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Dwyane Wade
Dwyane Wade 2011-8-15
How do I evaluate these expressions in terms of x?
1.) tan(2x-45degrees) 2.) sin(30degrees-3x)
also, how do I put the symbol for degrees? sorry im just new in matlab, thank you very much.

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回答（2 个）

Paulo Silva
Paulo Silva 2011-8-15
%make them anonymous functions
f1=@(x)tand(2*x-45) %notice that's not tan but tand, it uses degrees
f2=@(x)sind(30-3*x) %instead of radians
%evaluate at specific x values
x=0;
f1(x)
f2(x)
%plot them easily
subplot(211) %create one axes to show the first function
ezplot(f1) %you can define the x range like this ezplot(f1,[0 100])
subplot(212) %create another axes to show the second function
ezplot(f2) %ezplot(f2,[0 100]) -> this makes x start at 0 and finish at 100
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Paulo Silva
Paulo Silva 2011-8-15
Conversions
rad -> deg
180*x/pi
deg -> rad
pi*x/180
Fangjun Jiang
Fangjun Jiang 2011-8-15
You can't do degree*degree! Why not run an example?
x=90;
sind(x)
sind(2*x)

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Fangjun Jiang
Fangjun Jiang 2011-8-15
x=pi;
y=tan(2*x-pi*45/180)
z=sin(pi*30/180-3*x)
All the functions tan(), sin(), cos() etc use radius, you need to convert degree to radius.

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