Q12 / 71 · NTA Abhyas (JEE Main) 2020 · Mathematics · Inverse Trigonometric Functions

If the value of the expression tan⁡12cos-1⁡25 is in the form of a+ b where a, b∈Z, then the value of a+b b  is

Correct answer: 0.6

Solution

We know that,

tan⁡x2=1-cos⁡xsin⁡x 

∴  tan⁡12cos-1⁡25 =1-cos⁡cos-1⁡25sin⁡cos-1⁡25

=1-2/5sin⁡sin-1⁡1/5

=1-2/51/5=5-2

Now,  a+ b =−2+ 5

⇒a=−2 and b=5

Hence,  a+b b = 3 5 =0.6

Hence, the correct answer is 0.6.

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