# Simple Maths Causing a Issue

Discussion in 'Math' started by Ryaner, Jun 11, 2013.

1. ### Ryaner Thread Starter New Member

Dec 14, 2011
22
0
I can't get this question to work out at all.

Here is what is provided.

2.4638[cos(0.4964)-cos$\delta3$]-($\delta3$-0.4964)=0.0785

His final answer is,

2.4638cos$\delta3$+$\delta3$ = 2.5843

Can someone provide a step by step. Spent the last hour messing around with trying to get it to work out.

Its annoying cause I figured out all the integration he did and I get stuck on this.

2. ### Ryaner Thread Starter New Member

Dec 14, 2011
22
0
Figured it out. Happy days & god bless matlab

3. ### WBahn Moderator

Mar 31, 2012
17,757
4,800
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Don't be so quick to bless a piece of software for doing your thinking for you.

It has done you no favor. All it has let you do is slide a bit further along without addressing some very weak math skills. This will bite you sooner or later.

Here are the steps that evaded you so long. This is very basic math -- not even any algebra, really.

0) 2.4638[cos(0.4964) - cos(δ3)] - (δ3 - 0.4964) = 0.0785

1) 2.4638cos(0.4964) - 2.4638cos(δ3) - (δ3 - 0.4964) = 0.0785

2) 2.4638cos(0.4964) - 2.4638cos(δ3) - δ3 + 0.4964 = 0.0785

3) 2.4638cos(δ3) + δ3 = 2.4638*cos(0.4964) + 0.4964 - 0.0785

4) 2.4638cos(δ3) + δ3 = 2.4638*0.8793 + 0.4964 - 0.0785

5) 2.4638cos(δ3) + δ3 = 2.1664 + 0.4964 - 0.0785

6) 2.4638cos(δ3) + δ3 = 2.5843

I'm guessing that your problem was in not properly distributing the minus sign in going from Step 1 to Step 2 giving you a value of 1.5915 on the RHS in the final result.

Do yourself a favor -- take some time looking at this and figuring out exactly WHERE and WHY you weren't able to do this and reflect on what you could have done differently that would have allowed you to do it. Then adopt that as a normal practice!