# 10th Math Sample Paper 2019 | Q17 Choice 1

#### Section C | 3 Mark | Trigonometric Ratios

This 2019 CBSE class 10 Maths 3 mark question is from Trigonometry. An easy 3 mark question testing concepts in rewriting tan θ and cot θ in term of sin θ and cos θ and basic trigonometric identities.

Question 17A: Prove that cot θ – tan θ = $$frac{2 cos^2 θ – 1}{sin θ cos θ}$ ## Target Centum in CBSE 10th Maths #### Online CBSE Course online.maxtute.com ### Video Explanation ## NCERT Solution to Class 10 Maths #### With Videos ### Explanatory Answer | CBSE Sample Paper 2019 Question 17 Choice 1 LHS : cot θ – tan θ = $\frac{cos θ}{sin θ}$ - $\frac{sin θ}{cos θ}$ = $\frac{cos^2 θ – sin^2 θ}{sin θ cos θ}$ We know sin2 θ + cos 2 θ = 1 Rewrite sin2θ in the numerator as$1 - cos2θ): $$frac{cos^2 θ −$1− cos^2 θ$}{sin θ cos θ}) = $\frac{cos^2 θ − 1 + cos^2 θ}{sin θ cos θ}$
= $\frac{2 cos^2 θ – 1}{sin θ cos θ}$

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