Answer:
A, C
Step-by-step explanation:
Actually, those questions require us to develop those equations to derive into trigonometrical equations so that we can unveil them or not. Doing it only two alternatives, the other ones will not result in Trigonometrical Identities.
Examining
A) True

Double angle 
B) False,
No further development towards a Trig Identity
C) True
Double Angle Sine Formula 

D) False No further development towards a Trig Identity
![[sin(x)-cos(x)]^{2} =1+sin(2x)\\ sin^{2} (x)-2sin(x)cos(x)+cos^{2}x=1+2sinxcosx\\ \\sin^{2} (x)+cos^{2}x=1+4sin(x)cos(x)](https://tex.z-dn.net/?f=%5Bsin%28x%29-cos%28x%29%5D%5E%7B2%7D%20%3D1%2Bsin%282x%29%5C%5C%20sin%5E%7B2%7D%20%28x%29-2sin%28x%29cos%28x%29%2Bcos%5E%7B2%7Dx%3D1%2B2sinxcosx%5C%5C%20%5C%5Csin%5E%7B2%7D%20%28x%29%2Bcos%5E%7B2%7Dx%3D1%2B4sin%28x%29cos%28x%29)
Answer: 4
Step-by-step explanation: 2+2 is 4
Using the sinusoidal function, it is found that the temperature will be below 0ºC between May and August.
<h3>
What is a Sinusoidal function?</h3>
- A sinusoidal function is a function that depends on a trigonometric function, having peaks according to the period and amplitude given by this function.
The function for the average monthly temperature, in m months after January, is given by:

Working with elementary angles, we have that:





From this, we have that it becomes negative after March, and positive before September, removing the middle two options.
Now, we have to test for April and May, that is, m = 4 and m = 5, hence:


Negative only in May, hence the temperature will be below 0ºC between May and August.
To learn more about sinusoidal function, you can take a look at brainly.com/question/18055768
Answer:
b.
Step-by-step explanation:
hope it's help
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