The last big toughy

  • #1
Ok the last question on those pages of question is this and i have got stuck and cant figure it out. I need to show that (ds=degrees)
Sin(45ds+x) +cos(45ds+x) = sqaureroot2 cosx.
Ok so i did left side first and changed it to.
Sin45Cosy + Cos45Siny +Cos45Cosy - Sin45Siny
Now what i want to do is divide out the CosY and Sin Y but even if i do that it doesnt make square root two and i dont know what to do from there. Can you help me solve this last practise question.
 

Answers and Replies

  • #2
96
0
They've given you a trig problem that includes the sine and cosine of
a special angle. That should prod you in the right direction. If not, look at the attached text file.
 

Attachments

  • sincos.txt
    275 bytes · Views: 160
  • #3
HallsofIvy
Science Advisor
Homework Helper
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What you are doing doesn't make a whole lot of sense. What is Y?

sin(45+ x)= sin(45)cos(x)+ cos(45)sin(x) and
cos(45+ x)= cos(45)cos(x)- sin(45)sin(x).

Do you know what sin(45) and cos(45) are?

Plug those into the two equations above and add.
 
  • #4
Oh ok i get it, ya i thought of putting the 1/root2 in but wasnt sure how to go from there but i understand now. Thankyou so much!
 
  • #5
Originally posted by majinknight
Ok the last question on those pages of question is this and i have got stuck and cant figure it out. I need to show that (ds=degrees)
Sin(45ds+x) +cos(45ds+x) = sqaureroot2 cosx.
Ok so i did left side first and changed it to.
Sin45Cosy + Cos45Siny +Cos45Cosy - Sin45Siny
Now what i want to do is divide out the CosY and Sin Y but even if i do that it doesnt make square root two and i dont know what to do from there. Can you help me solve this last practise question.


how old are you buddy?
 
  • #6
16 currently in grade 11. Why?
 
  • #7
695
0


Originally posted by PrudensOptimus
how old are you buddy?

Haven't you discovered the "Profile" button yet, buddy? :)
 
  • #8
45
0
Just testing out the "math typesetting" thing:

[tex]
\begin{align*}
\sin(45^\circ + x) &= \sin(45^\circ) \cos x + \cos(45^\circ) \sin x \\
&= \frac{\cos x}{\sqrt{2}} + \frac{\sin x}{\sqrt{2}} \\
&= \frac{\cos x + \sin x}{\sqrt{2}}
\end{align*}
[/tex]
 
  • #9
Originally posted by majinknight
16 currently in grade 11. Why?


lol which state are you in?
 
  • #10
Im in Ontario Canada. Its a province not a state.
 
  • #11
4
0
are you in the canadian school system?
 
  • #12
Yes i am, i am glad you are all so interested in me. I feel so special :wink:
 
  • #13
4
0
heh, it sounded alot like one of our A-level questions, i was curious about it. :wink:
 

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