# cosine

1. ### Hi, I have tried to work out the following...

...can someone help me. Sine cosine tangent angles i have attached the following thanks in advance!
2. ### Convolution of cos and rect

I am asked to find the convolution of \beta * L where \beta(x)=\begin{cases} \frac{\pi}{4a}\cos\left(\frac{\pi x}{2a}\right) & \left|x\right|<a\\ 0 & \left|x\right|\geq a \end{cases} L(x)=\begin{cases} 1 & \left|x\right|<1\\ 0 & \left|x\right|\geq 1 \end{cases} Knowing that...
3. ### Need trig help?

I take all of my classes online, so I don't have the opportunity for in class help and this is really kicking up my anxiety, because I'm not understanding anything about this, or any of the concepts. 1. Your family rents cottage on the ocean for a week one summer. you notice that the tide...
4. ### Discrete Cosine Transformation

Hi all, I'm an undergrad from brazil. While I was fumbing around with a C++ implementation of DCT (discrete cosine transform - II : https://en.wikipedia.org/wiki/Discrete_cosine_transform#DCT-II) I stumbled upon something: DCT(X) * DCT(Y) = A* X*Y where X and Y are vectors. Let me demonstrate...
5. ### half range cosine series

i am asked to find the half range cosine series for f(x) = cos x , 0<x < (π/2 ) but , i dont understand the working provided by the author , Can someone explain how to transform the upper circled part to lower circled part ?
6. ### Addition/subtraction formulas for sine or cosine to simplify the following

cos(3pi/10)cos(pi/5)-sin(3pi/10)sin(pi/5) factor cos and sin and get common denominators and combine: cos(5pi/10)-sin(5pi/10) cosine(90 degrees)-sin(90 degrees) 0-1 answer is -1? Am I correct? Wait I see the formula for this is : cos(a+b) so then I do cos(3pi/10+pi/5) cos(5pi/10) and...
7. ### Fourier cosine series

why the author need to differentiate the a1 using L'hopital rule ? the working already showed that the a1 = 0 , am I right ?
8. ### Not quite sure what I did wrong. Cosine equation

Okay, so we were ask to find all solutions for cos(t)=.72 and round to 2 decimal places where appropriate. I got .77+2pi and 2pi-.77+2pi but that not right. So, whats the right answer. Thanks in advance.
9. ### Trigonometric Integrals: Odd power of cosine

The tittle should have said Odd power of sine, not cosine..... Please click on the image for my question. Thanks!
10. ### Cosine Function question?

Hi please show me how to do this problem i don't know how to get started. Thank you so much!!! The carnival has come to town with a ferris wheel that has a radius of 30 feet. People get on when the passenger compartments are at their lowest, 2 feet off the ground. The wheel makes a full...
11. ### Power series for Cosine

Find the power series for f(x)=cos(sqrt(x)) anyone know how to go about doing this problem?
12. ### help with tan, sine, and cosine word problems!!!

I am having trouble understanding these following questions. could someone please solve them for me? i need the trig function(s) and a diagram to go with it. if you cant make a diagram just solve it for me that would be helpful. 1. A tree is broken by the wind. The top touches the ground 13...
13. ### law of cosine problem

Hi everyone, I just joined the forums and was wondering if i could get some help with a math problem on my homework assignment, I just can't seem to figure it out it goes like this In ΔABC, suppose that a4 + b4 + c4 = 2(a2 + b2)c2. Find ∠C. (There are two answers. Enter your answers as a...
14. ### Discrete Cosine Transform

Hello, I'm trying to understand the 2D-DCT (Discrete Cosine Transform) and it is giving me some trouble. I think I understand the logic. The summation is representative of "loops" whereby the function f(x,y) (spatial domain) undergoes the transformation. The problem I have is that I cannot see...
15. ### Proof sin(θ)=cos(θ) when...

I know that adjacent side should be equal to opposite which happens at $\dfrac{\pi}{4}$ and $\dfrac{5\pi}{4}$ (plus coterminal angles); the quadrants are 1 and 3 because signs of sin and cos thus coincide. I'm not sure that proves it though? How do I go about this? I don't think the proof should...
16. ### Cosine Graph help (pic included)

Need help finding the new equation of this graph Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting link just in case you can't see the picture. Thanks in advance.
17. ### HELP!!lowering power in terms of the first power of cosine [(cosx)^4][(sinx)^4]

I really got trouble w/ whole lowering powers thing! need help on this one:[(cosx)^4][(sinx)^4]
18. ### Sine and cosine rules

Hi, In a triangle where only the sides are given, one uses the cosine rule to find an angle. However, having done so, is it then possible to use the sine rule to find another angle? Apologies in advance if the question is dumb.(Angry) Thank you and go well.
19. ### Functions, Statistics, Trigonometry Questions?

Write a function whose parent is y=sin x and whose graph has amplitude 3/4 and period pi Give a general solution to cos^2 theta=3/4 What are the period, amplitude, and shifts of the graph y= 3 cos (2x-pi) +5 from y=cos x Thank you!!
20. ### Using two vectors to prove cosine identity

The two vectors a and b lie in the xy plane and make angles \alpha and \beta with the x-axis. By evaluating a \cdot b in two ways prove the well known trig identity: \cos (\alpha + \beta) = \cos \alpha \cos \beta + \sin \alpha \sin \beta So I drew a diagram of what it describes but it...