Question Details

Find the value of sin-1⁡(35)+sin-1⁡(45)+cos-1⁡(3√2)

Options

A

π/3

B

2π/3

C

4π/3

D

π/4

Correct Answer :

2π/3

Solution :

The correct option is 2π/3.

To find the value of the given expression, let us first identify and clarify the standard mathematical representation of the terms in the expression:
1. The term sin1(35) represents the inverse sine function sin135.
2. The term sin1(45) represents sin145.
3. The term cos1(32) represents cos132.

Substituting these clarified terms, the expression becomes:
E=sin135+sin145+cos132

Step 1: Simplify the first two terms
Let θ=sin145. This means that:
sin(θ)=45

Using the fundamental trigonometric identity sin2(θ)+cos2(θ)=1, we can find cos(θ):
cos(θ)=1sin2(θ)=1452=11625=925=35

Therefore, we have:
θ=cos135

This shows that:
sin145=cos135

Now, substitute this back into the sum of the first two terms:
sin135+sin145=sin135+cos135

Using the standard identity sin1(x)+cos1(x)=π2 (for |x|1), we get:
sin135+cos135=π2

Step 2: Evaluate the third term
Next, we evaluate:
cos132

Since cosπ6=32, we have:
cos132=π6

Step 3: Combine all terms
Adding the simplified values together:
E=π2+π6

Find a common denominator to sum the fractions:
E=3π6+π6=4π6=2π3

Thus, the final value of the expression is 2π3.

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