Answer:
Step-by-step explanation:
Use the half angle identity for cosine:
cos(x/2)=+ or - sqrt(1+cos(x))/sqrt(2)
I'm going to figure out the sign part first for cos(x/2)...
so x is in third quadrant which puts x between 180 and 270
if we half x, x/2 this puts us between 90 and 135 (that's the second quadrant)
cosine is negative in the second quadrant
so we know that
cos(x/2)=-sqrt(1+cos(x))/sqrt(2)
Now we need cos(x)... since we are in the third quadrant cos(x) is negative...
If you draw a reference triangle sin(x)=3/5 you should see that cos(x)=4/5 ... but again cos(x)=-4/5 since we are in the third quadrant.
So let's plug it in:
cos(x/2)=-sqrt(1+4/5)/sqrt(2)
No one likes compound fractions (mini-fractions inside bigger fractions)
Multiply top and bottom inside the square roots by 5.
cos(x/2)=-sqrt(5+4)/sqrt(10)
cos(x/2)=-sqrt(9)/sqrt(10)
cos(x/2)=-3/sqrt(10)
Rationalize the denominator
cos(x/2)=-3sqrt(10)/10
Answer:i can's see it very well sorry kid
12
Step-by-step explanation:i dont know
Hey there!
It seems your problem is simply trying to rewrite the sentence.
Let's rewrite our sentence, from the phrase after the comma to the phrase before the comma.
Essentially, we are just flipping the sentence structure.
It should be this:
The two angles are complementary if the sum of the two angles are 90 degrees.
Let's take a good look at our answers.
A.) There are two angles.
While this is a true statement, it's a little too vague to understand. We can eliminate this answer choice.
B.) The sum of two angles is 90 degrees.
This is also a true statement, but it doesn't describe what type of angles sum to 90 degrees, so we can eliminate this as well.
C.) The angles are complementary.
This is similar to answer choice A. It's a little too vague for specific understanding. We can eliminate this answer choice.
D.) Angles are complementary if their sum is 90 degrees.
This is an accurate statement, and provides details to support it's claim, also rewriting the original sentences into one properly. This answer choice is correct.
Your answer is D.)
I hope this helps!
Answer:
D
Step-by-step explanation:
Using Pythagoras' identity in the right triangle
The square oh the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
h² = (9
)² + (9 )² = 162 + 162 = 324 ( take the square root of both sides )
h = 
= 18 → D
