Why isn't my code working?

Question

Collin Kerr 2016-4-18

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评论： James Tursa 2016-4-19

%8 to 15 meters is the range 
%Velocity is 0,15,30,45,60,75,90
clc,clear
F = input('Targeted Distance = ');
V_o = input('Velocity at launch = ');
S_o = input('Elevation angle at launch = ');
a=9.81;                     %Its a given
b=V_o*sind(S_o)             %It makes the coding a bit less confusing.
c=0;                        %Also a given
fprintf('The targeted distance for the launch is %d meters. \n', F)
fprintf('The velocity for the launch is %d meters per second. \n', V_o)
fprintf('The elevation angle for the launch is %d degrees. \n', S_o)
Q1=(-b-sqrt(b^2-4*a*c))/2*a;
disp(Q1)

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Collin Kerr 2016-4-18

编辑：Collin Kerr 2016-4-18

The answer is .264 I don't understand why its not working. The inputs to put in are V_o as 5 and S_o as 15. F is not important at this time.

James Tursa 2016-4-19

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Answer 1

James Tursa 2016-4-19

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You need to enclose the denominator in parentheses:

Q1=(-b-sqrt(b^2-4*a*c))/(2*a);

The way you have it coded, since / and * have the same precedence the operations are performed left to right and MATLAB sees your current coded expression as:

Q1=((-b-sqrt(b^2-4*a*c))/2) * a;

Which is not what you wanted.