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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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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Accepted Answer

Image Analyst
Image Analyst on 16 Oct 2020
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);

More Answers (1)

meghannmarie
meghannmarie on 16 Oct 2020
Edited: meghannmarie on 16 Oct 2020
You need to use the dot operator if you are doing element wise multiplication (.*). You use just the asterick for matrix multiplication.
triangle= area.*b

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