CoM reduced by total body height when bending your knee X degrees

AI Thread Summary
When a man with a standing height of 185cm bends his knee at 30 degrees, the reduction in height can be calculated using trigonometry, specifically considering the lengths of the femur and tibia. Participants in the discussion emphasize the importance of showing calculations to identify errors and improve understanding. There is a suggestion to create a sketch to visualize the problem better. The conversation highlights the intersection of mathematics and biology in solving the question. Overall, the thread seeks to clarify how to accurately determine the height reduction when bending the knee.
Pushies
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Lets say that a man with a standing height of 185cm bent his knee 30 degrees, how many centimeters will be reduced from his standing height? Assume his femur length is 60cm and his tibia (shin) length is 50cm.

Can anyone give me a hint?
I've tried to use trigonometry but i don't think i fully understand the rules of trigonometry because my answer doesn't make sense and I am afraid to show my calculations here because it looks too dumb.

Thanks in advance.
 
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Hello, and :welcome: !

PF rules require you to post an effort nonetheless; or we are not allowed to assist.
Better come up with at least a clarifying sketch before a mentor removes your thread !
Good chance you'll see the light when you make the sketch !

Oh, and: good you're not asked to say anything about the center of mass -- standing height is a lot easier :wink: !
 
How can we determine what went wrong if you don't show your calculations?

As this is a homework-like question I moved the thread to our homework section.
 
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Pushies said:
im afraid to show my calculations here because it looks too dumb.
Compared with thinking we can tell you where you are going wrong without seeing your attempt?
 
Pushies said:
Lets say that a man with a standing height of 185cm bent his knee 30 degrees, how many centimeters will be reduced from his standing height? Assume his femur length is 60cm and his tibia (shin) length is 50cm.

Can anyone give me a hint?
I've tried to use trigonometry but i don't think i fully understand the rules of trigonometry because my answer doesn't make sense and I am afraid to show my calculations here because it looks too dumb.

Thanks in advance.
Is this question a combo of maths and biology?😂😂
 

Thread 'Find the polar form of a complex number'

The working out suggests first equating ## \sqrt{i} = x + iy ## and suggests that squaring and equating real and imaginary parts of both sides results in ## \sqrt{i} = \pm (1+i)/ \sqrt{2} ## Squaring both sides results in: $$ i = (x + iy)^2 $$ $$ i = x^2 + 2ixy -y^2 $$ equating real parts gives $$ x^2 - y^2 = 0 $$ $$ (x+y)(x-y) = 0 $$ $$ x = \pm y $$ equating imaginary parts gives: $$ i = 2ixy $$ $$ 2xy = 1 $$ I'm not really sure how to proceed from here.
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