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

[howsaboutno]

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!

 

[mgb_phys]

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

 

[HallsofIvy]

Are there parentheses in the problem that you didn't include here?

 

[howsaboutno]

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.

 

[mathman]

Something doesn't look right. Sin(theta2)=-.913. Therefore theta2 = -66 or -114 (deg.)

 

[howsaboutno]

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.

 

[mathman]

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.