Learn in your speed, with individual attention - Teachoo Maths 1-on-1 Class

Ex 8.3

Ex 8.3, 1

Ex 8.3, 2 Important

Ex 8.3, 3 (i) [MCQ]

Ex 8.3, 3 (ii) [MCQ] Important

Ex 8.3, 3 (iii) [MCQ] Important

Ex 8.3, 3 (iv) [MCQ]

Ex 8.3, 4 (i) Important

Ex 8.3, 4 (ii)

Ex 8.3, 4 (iii) Important

Ex 8.3, 4 (iv) Important

Ex 8.3, 4 (v) Important

Ex 8.3, 4 (vi)

Ex 8.3, 4 (vii) Important You are here

Ex 8.3, 4 (viii)

Ex 8.3, 4 (ix) Important

Ex 8.3, 4 (x)

Question 1 (i) Important Deleted for CBSE Board 2024 Exams

Question 1 (ii) Deleted for CBSE Board 2024 Exams

Last updated at Aug. 16, 2023 by Teachoo

Ex 8.3, 4 Prove the following identities, where the angles involved are acute angles for which the expressions are defined. (vii) (sin θ − 2 sin3 θ)/(2 cos3 θ − cos θ)=tan θ Solving L.H.S (sin θ − 2 sin3θ)/(2 cos3 θ − cosθ) = (𝒔𝒊𝒏𝜽 (1 − 2 sin2 θ))/(𝐜𝐨𝐬 𝛉(2cos2 θ − 1)) = sinθ/(cos θ) × ( (1 − 2sin2θ))/((2cos2θ − 1)) = tan θ × ( (1 − 2sin2θ))/((2𝐜𝐨𝐬𝟐𝛉 − 1)) We know that cos2 θ + sin2 θ = 1 cos2 θ = 1 – sin2 θ = tan θ × ((1 − 2sin2θ))/((2(𝟏 − 𝐬𝐢𝐧𝟐𝜽) −1) ) = tan θ × ((1 − 2sin2θ))/((2 − 2sin2θ − 1)) = tan θ × ((𝟏 − 𝟐𝐬𝐢𝐧𝟐𝛉))/((𝟏 − 𝟐𝐬𝐢𝐧𝟐𝛉) ) = tan θ × 1 = tan θ = R.H.S Hence proved