Question Details

Considering only the principal values of the inverse trigonometric functions, evaluate:


cot 1 ( cot ( 11 ) ) + 10 sin (2 cos ( 1 ( 1 /2 ))+ 10 sin 2 tan 1 ( 2 )

Options

A

3π+7

B

7

C

4π+7

D

3π5

Show Answer

Correct Answer :

Option C

4π+7

Solution :

`. Let's double-check all MathML in the solution to ensure no HTML entities for minus, and no `display="block"`. Everything is clean and straightforward. Let's write out the response. 4π+7

The correct option is 4π+7.

To evaluate the given expression using the principal values of the inverse trigonometric functions, we break the expression into three separate terms:

E=cot-1(cot(-11))+10sin2cos-112+10sin2tan-1(2)

Step 1: Evaluate the first term, T1=cot-1(cot(-11))

Recall that the principal value branch of cot-1(x) is (0,π).

We know that cotangent is periodic with period π, so cot(-11)=cot(4π-11).

Since π3.14159, we have 4π12.56637.

Therefore, 4π-111.56637, which lies in the principal interval (0,π).

Hence:

T1=cot-1(cot(4π-11))=4π-11

Step 2: Evaluate the second term, T2=10sin2cos-112

The principal value of cos-112 is π4.

Substituting this value in:

T2=10sin2×π4=10sinπ2

Since sinπ2=1:

T2=10×1=10

Step 3: Evaluate the third term, T3=10sin2tan-1(2)

Let θ=tan-1(2), so that tan(θ)=2.

Using the double-angle identity for sine in terms of tangent:

sin(2θ)=2tan(θ)1+tan2(θ)=2(2)1+22=45

Therefore:

T3=10×45=8

Step 4: Combine all terms

Adding the results of the three terms together:

E=T1+T2+T3=(4π-11)+10+8

E=4π-11+18=4π+7

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