As you know, swollen tonsils cause fever and a muscular ache.

영어에서는, article이 있어야 되요. 명사앞에서요. 여기서 명사가 fever와 ache이잖아요. 근데 선택할 article이 2구지가 있다: a와 the.

하나 밖에 없을 경우엔 the
여러가지 가운데서 아무거나 / 많은 종류중에서 한 가지 형 : a [ CAUSE A FEVER ] (몇도까지, 얼마나 심한지 fever은 몇가지 형이 있어요)
모두 다: 명사 + s ... [ACHES] (복수니까, article 빼고 +s)

this applies to the specification, especially, the background art section. There is too much use of 'a' instead of 'the' when there is ONLY ONE OPTION for a thing. Because, where there is ONLY ONE OPTION you must use 'the'.

1. which sets and controls surrounding conditions, such as a² temperature (x)

   ²There can only be one temperature, this should be THE. This should be the even if it is in the body of the specification.

   which sets and controls surrounding conditions, such as the temperature (o)

2. which sets and controls surrounding conditions, such as a temperature, a humidity (x)
   

I wanted to point out an error that is extremely common in the BACKGROUND OF THE INVENTION part of the patent document, when introducing the art. I have corrected and keep correcting these, and will forever be correcting these unless I explain why the correction is required, so you can learn, and improve your writing.

These 2 are in fact different:

(1) -- a device
(2) -- devices

They often appear in the first section of the patent document, in a sentence such as

(A) A machine for doing X typically is Y. (x)

This is incorrect, and should be

(B) Machines for doing X typically are Y. (o)

(1) That is _________ Jason’s book.

No article.

Examples of proper nouns are:
Shinhan Bank
Starbucks
Tous Les Jours (the name of a bakery)

(1) _____ ¹ Maxwell’s fourth equation, related to electromagnetic waves, states that a magnetic force² always forms a closed loop.

¹ Maxwell's fourth equation does not require an article, it is a proper noun. If it were just a normal noun, then it would require one because the last word is equation.
² a magnetic force == a specific instance of a magnetic force, so that in this case an article is required though magnetic force can also be used as an asbstract scientific notion in which case it would not take an article.