Solving A=cos(-20)-K1-K2cos(-20)+K3 - Get Help Here

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Discussion Overview

The discussion revolves around solving the equations A=cos(-20)-K1-K2cos(-20)+K3 and B=-2sin(-20) within the context of a 4 bar mechanism. Participants are attempting to determine the correct values for A and B given specific constants and an angle.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant expresses difficulty in calculating A, stating that despite using both radians and degrees, they cannot achieve the expected result of 2.922.
  • Another participant suggests that the angles are likely in degrees and recommends checking the order of operations, implying that the calculations may have been done incorrectly.
  • A question is raised about the potential omission of parentheses in the original equation, which could affect the outcome.
  • Further clarification is provided regarding the equations, indicating that theta2 is -20, and that the equations relate to a 4 bar mechanism.
  • One participant points out a discrepancy in the sine calculation, noting that sin(theta2) results in -0.913, leading to possible angles of -66 or -114 degrees.
  • Another participant emphasizes that -2sin(theta2) is the relevant term for the problem, indicating confusion over why the cosine equation does not yield the correct answer while the sine equation does.
  • A suggestion is made to divide the value of -2sin(theta2) by -2 to find the corresponding value.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct approach to solving the equations, and multiple viewpoints regarding the calculations and interpretations of the equations remain present.

Contextual Notes

There are indications of potential misunderstandings regarding the order of operations and the inclusion of parentheses, which may affect the calculations. Additionally, the discussion highlights the reliance on specific angle measures and their implications for the equations.

howsaboutno
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hello i am stuck on the following:

A=cos(-20)-K1-K2cos(-20)+K3

K1=3.825
K2=2.295
K3=2.514

A should equal 2.922 but somehow i can't get it to equal that i have tried using my calc in radians and degrees mode but neither come out with the right answer please help me!
 
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The angles are almost certainly in degrees from their size.
I suspect that you (or the calculator) are doing the sums in the wrong order.
Write down each term as a number.
then remember the order:
Brackets
Division
Multiplication
Addition
Subtraction

ps. Have you copied it down correctly, I get -2.52
cos(20) is roughly 1 so you have A=k3-(k1+k2) = 3.8-4.8 which is negative
 
Last edited:
Are there parentheses in the problem that you didn't include here?
 
hello again well another part of it is that

B=-2sin(-20) and B=1.826

which is right you see this equation and the other one are to do with a 4 bar mechanism

also i have put the correct value -20 for the equations because original the equations are
A=cos(theta2)-K1-K2cos(theta2)+K3
and
B=-2sin(theta2)

theta 2 is -20.
 
Something doesn't look right. Sin(theta2)=-.913. Therefore theta2 = -66 or -114 (deg.)
 
mathman said:
Something doesn't look right. Sin(theta2)=-.913. Therefore theta2 = -66 or -114 (deg.)

so sin(theta2) isn't part of the problem -2sin(theta2) is!

but i understand the -2sin(theta2) its the other equation with cos i don't understand why i don't get the right answer cause i get the right answer for the equation with sin but not the equation with cos.
 
howsaboutno said:
so sin(theta2) isn't part of the problem -2sin(theta2) is!

but i understand the -2sin(theta2) its the other equation with cos i don't understand why i don't get the right answer cause i get the right answer for the equation with sin but not the equation with cos.

-2sin(theta2)=1.826. Now divide by -2.
 

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