I have a task where I have to calculate the area of a triangle from degrees 1 to 90, that is bound within a semi circle. I keep getting an error with the last line for some reason

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Beenish Shabir 2020-10-16

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评论： Rena Berman 2021-5-7

I have a task where I have to calculate the area of a triangle from degrees 1 to 90, that is bound within a semi circle. I keep getting an error with the last line for some reason.

radius = rand;
a = 2*radius;
alpha = (1:90)
b = a * cosd(alpha(1:90));
area = 0.5*a*sind(1:90)
triangle= area*b

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Rik 2020-10-19

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Question originally posted by Beenish Shabir (retrieved from Google cache):

I have a task where I have to calculate the area of a triangle from degrees 1 to 90, that is bound within a semi circle. I keep getting an error with the last line for some reason

I have a task where I have to calculate the area of a triangle from degrees 1 to 90, that is bound within a semi circle. I keep getting an error with the last line for some reason.

radius = rand;
a = 2*radius;
alpha = (1:90)
b = a * cosd(alpha(1:90));
area = 0.5*a*sind(1:90)
triangle= area*b

Rena Berman 2021-5-7

(Answers Dev) Restored edit

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Answer 1

Image Analyst 2020-10-16

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You need to be using .* instead of * to do an elemenet by element multiplication instead of a matrix multiplication. Try this:

radius = 2 * rand;
alpha = (1:90)
bases = radius * cosd(alpha) % A vector of 90 elements
heights = radius * sind(alpha) % A vector of 90 elements
triangle_areas = 0.5 * bases .* heights % A vector of 90 elements
% For optional fun, plot the area.
plot(alpha, triangle_areas, 'b.-', 'LineWidth', 2);
grid on;
xlabel('Angle', 'FontSize', 18);
ylabel('Area', 'FontSize', 18);
title('Triangle Area vs. Angle', 'FontSize', 18);

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Beenish Shabir 2020-10-17

Thank you so much!! You are such a life saver :)

Image Analyst 2020-10-17

You can Accept only one answer, so accept the best one. However you can also vote for that and the other(s) to award those persons additional reputation points also.

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