18652 questions

How can you tell the environment a sedimentary rock is deposited in?

The first stage in the formation of a sedimentary rock is the deposition of sediment. The size, shape and type of sediment can tell you lots about the depositional environment. In a high energy environment, such as a river bed, currents are able to carry large particles. When the current loses energy, these will be deposited. Low energy currents cannot carry large particles, and so fine grained rocks form in a low energy environment. As particles are transported, they are constantly eroded, decreasing the size of particles and increasing their roundness. Particles that have been transported contain well rounded particles or hard minerals such as quartz. These rocks are said to be more mature. If particles have not been transported as far, particles will be more angular, and softer, more easily destroyed minerals such as feldspar may still be present.
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Holly U.

Answered by Holly, Geology tutor with MyTutor

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How can I prove that an angle in a semi-circle is always 90 degrees?

If we take the diameter of a circle and create an angle on the circumference at point C of the circle from the two points where the diameter meets the circumference (points A and B), the angle created will always equal 90 degrees. To prove this we can draw a line from point C to the centre (point O). We have now created two isosceles triangles (O,A,C) and (O,B,C). Therefore, angle OAC = angle OCA (we will call this angle x) and angle OBC = OBA (we will call this angle y).Our angle at point C, therefore is equal to x+y.We can now return to the original triangle (A,B,C) and using our triangle knowledge we can say:x+y+(x+y)=1802x+2y=180x+y=90
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David W.

Answered by David, Maths tutor with MyTutor


Find the partial fraction decomposition of the expression: (4x^2 + x -64)/((x+2)(x-3)(x-4)).

The first step to solving this question is inputting our dummy variables, and laying out the question so we know what we're doing.
So we end up with:(4x2 + x - 64)/((x+2)(x-3)(x-4)) = A/(x+2) + B/(x-3) + C/(x-4).
The next step is to clean up this equation and make it a bit easier to substitute values into it. This is done by multiplying each side through by the denominator.
4x2 + x - 64 = A(x-4)(x-3) + B(x+2)(x-4) + C(x+2)(x-3).
We know that this expression needs to hold for every value of x. This means that we can cherry pick values of x to try and gain information about our unknowns.
The first case is x = -2.
So we substitute x = -2 in and end up with:
4(-2)2 - 2 - 64 = A(-2-4)(-2-3) + B(-2+2)(-2-4) + C(-2+2)(-2-3).
Choosing x = -2 as the value to look at has the advantage of turning any (x+2) factors into a 0. This means that both B and C now have 0 as their coefficient. This means that A will be our only variable, and we can solve for it easily.
16 - 2 - 64 = A(-6)(-5).
-50 = 30A.
A = -5/3.
Our next two cases are x = 3 and x = 4. These are solved in a similar way to the x = -2 case.
Once substituted into the expression x = 3 gives a value of B = 5, and x = 4 gives a value of C = 2/3.The last step is to substitute these back into our original expression, which gives an answer of:
(4x2 + x - 64)/((x+2)(x-3)(x-4)) = -5/3(x+2) + 5/(x-3) + 2/3(x-4).
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Matt V.

Answered by Matt, Maths tutor with MyTutor


What is the perfect tense and how do you form it?

The perfect tense in Spanish translates as 'to have done something' in English. It is used to express actions that begun in the past and are carried through to the present. For example, 'Todavía no ha traído los libros'/'She hasn't brought the books yet.' She did not bring the books in the past, and she still has not brought them in the present. It is also used for events which took place in the very recent past (usually that day). For example, 'Esta mañana no he desayunado'/'I didn't have breakfast this morning.' In this instance, the fact that I did not have breakfast this morning is still relevant to the present conversation, where presumably someone has asked me whether I did.
This tense is formed using the auxiliary verb 'haber' (has) and the past participle of the verb (e.g. eaten). Haber is conjugated like this: he, has, ha, hemos, habéis, han. The past participle is formed differently for -ar, -er and -ir verbs. For -ar verbs we add -ado to the verb stem, for example, llamar--> llamado; for -er and -ir verbs we add -ido to the verb stem, for example, comer--> comido and dormir--> dormido. There are also some irregular past participles. Some of the most common ones are: abrir--> abierto, morir--> muerto, romper--> roto, escribir--> escrito, ver--> visto, and volver--> vuelto.
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Lexi R.

Answered by Lexi, Spanish tutor with MyTutor


How do I analyse quotes in an essay?

The first thing to do when choosing a quote to analyse in an essay in to make sure it is relevant to your argument. Think about the theme in the question you have been set - for example, a question asking you to analyse the presentation of women in a text will be looking for quotes with the theme of gender. Decide whether you are for or against this argument, and then select quotes that back up your point. Examiners are looking for a point, evidence, explanation/analysis and then a link that ties the point back to the overall argument of your essay. The quote falls under the evidence bullet point in the checklist.

Once you have selected your quote, a sophisticated technique to impress examiners and introduce your analysis is to embed it. For example, introduce your paragraph with a topic sentence, eg. "The presentation of women in Jane Eyre arguably challenges the female stereotypes of the time" and then embed the quote "for example, when Jane says 'I am no bird; and no net ensnares me' she defies the Victorian confinement of women." This opens up the gate for further analysis, and sounds better than just listing quotes by themselves which often leads to the point and relevance getting lost. Now you have introduced the quote in your paragraph, you need to pick it apart. One way to go about this is to start with close reading and then expand with the broad connotations of what this could mean in the greater scale of the text and your argument. Some ideas for close reading is to discuss literary techniques the author uses, whether or not it is typical/atypical of the genre and how these techniques contribute to the meaning of the quote. For example "I am no bird" is a metaphor, and this contributes to a bigger theme of women often being objectified as wild creatures to be captured and tamed. Then you can start to discuss context - that is, how the quote is relevant to the issues of society at the time. For example, Jane Eyre was written in the Victorian era, a time that was still very much patriarchal.

Finally, after some analysis, make sure to link back to your topic sentence. This neatly ties the quote to the point and keeps in relevant to your essay by not allowing yourself to go on a tangent. Repeat these steps and link relevant quotes together in a similar way, and you will create sustained evidence for your points!
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Megan M W.

Answered by Megan M, English tutor with MyTutor


Solve the simultaneous equations: 2x+5y=25, x=y+2

using our second equation, we can see that x=y+2. Therefore we can sub x into the first equation. This will give us 2*(y+2)+5y=25. We can go ahead and expand the brackets, which gives us 2y+4+5y=25. We can combine the y terms which gives 7y+4=25. We can take 4 away from both sides with gives 7y=21, and divide both sides by 7 so y=3. We can sub 3 into y in the original equation, to give that x=5.
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Louis W.

Answered by Louis, Maths tutor with MyTutor


Compare the views of Sources A and B about commemoration and remembrance.

Sources A and B both agree to a broad extent about the agreement on the site of the Scottish National War memorial and it should be in the capital city, Edinburgh. Secondly, Sources A and B also agree on how the original plan was altered and the importance of Scots in its planning, construction and financing.Overall both sources correlate and agree on how important such a memorial is to acknowledge Scottish sacrifice during the war.(We can also take an approach usually for this question in other cases where it may be suitable)
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Megan C.

Answered by Megan, History tutor with MyTutor


Find a quarter of the area of a circle with a diameter of 10cm.

To find a part of the area we need the whole area first.
Find the formula for the area of a circle: A= pi x r2
We have been given the diameter so we need to work out what the radius is, half of the diameter so r = 5cm.
Now use the formula for the area to find the area of the whole circle on your calculator: A = pi x 52 = 78.54cm2
The final step is to now find the fraction of the circle that is asked for.
To do this we simply multiply the whole area by the fraction that they want so in this case we need to do 1/4 x 78.54 = 19.64cm2 cm2 (2dp)
Remember not to forget the units and it is good to write down what you have rounded the answer to, in this case 2 decimal places.

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Joseph S.

Answered by Joseph, who has applied to tutor Maths with MyTutor

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