
Find the value of the following.
Answer
440.1k+ views
Hint: Since it is not possible to find the angles of the trigonometric function individually, try to bring those angles in the form of the angles which are easily available to us or which we can find out easily.
Complete step-by-step answer:
We have to find the value of a trigonometric function of the angle . Since we directly do not know the value of the given angle. We will try to use some already known trigonometric identities to find the answer of the question given.
We know that . So, we will use this identity to represent in terms of . We observe that,
On using the identity we get,
So, we will try to find the value of . Let us take to be , that is .
Then we can see that .
Now on applying sine function to the angles on both sides of the equation we get,
Now again by using the identity , we get
Now we will use the identities for multiple angles to get,
[Using and ]
Since , we have
[Using ]
, which is a quadratic equation in . So, we use the quadratic formula given for the equation .
Therefore,
Since belongs to the first quadrant, we know that is positive.
Therefore, .
So, we have .
Hence the value of is .
So, the correct answer is “ ”.
Note: While solving this kind of problem, one should remember that three are many ways of getting to the answer using various trigonometric identities. But we have to be clear with what we need to find and use a relatively easier method. Remember to mention the identities used wherever required. Such as etc.
Complete step-by-step answer:
We have to find the value of a trigonometric function of the angle
We know that
On using the identity
So, we will try to find the value of
Then we can see that
Now on applying sine function to the angles on both sides of the equation we get,
Now again by using the identity
Now we will use the identities for multiple angles to get,
Since
Therefore,
Since
Therefore,
So, we have
Hence the value of
So, the correct answer is “
Note: While solving this kind of problem, one should remember that three are many ways of getting to the answer using various trigonometric identities. But we have to be clear with what we need to find and use a relatively easier method. Remember to mention the identities used wherever required. Such as
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