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Inverse Trigonometric Functions · Question 106 of 120

Question 106

MediumOriginal question

What is the value of sec⁡2(tan⁡−12)+cosec⁡2(cot⁡−13)\sec^{2}\left(\tan^{-1} 2\right) + \operatorname{cosec}^{2}\left(\cot^{-1} 3\right)?

Options for question 106

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. sec⁡2θ=1+tan⁡2θ\sec^{2} \theta = 1 + \tan^{2} \theta, so sec⁡2(tan⁡−12)=1+4=5\sec^{2}\left(\tan^{-1} 2\right) = 1 + 4 = 5.

  2. cosec⁡2ϕ=1+cot⁡2ϕ\operatorname{cosec}^{2} \phi = 1 + \cot^{2} \phi, so cosec⁡2(cot⁡−13)=1+9=10\operatorname{cosec}^{2}\left(\cot^{-1} 3\right) = 1 + 9 = 10; the sum is 15.

Worth noting

13 adds only tan⁡2\tan^{2} and cot⁡2\cot^{2}, 4+94 + 9, dropping the 1 in each identity.

Concept
A function of a principal value
Typical time
90 s
Your time
—
The rule this testsValues of expressions
Practise this chapter →

Ten questions from Inverse Trigonometric Functions, at your own pace.

Practise this chapter →

Ten questions from Inverse Trigonometric Functions, at your own pace.