If cos⁡θ + cos⁡ 2 θ = 1, the value of sin 2 ⁡θ + sin 4 ⁡θ is
(a) -1 (b) 0 (c) 1 (d) 2
CBSE Class 10 Sample Paper for 2022 Boards - Maths Basic [MCQ]
CBSE Class 10 Sample Paper for 2022 Boards - Maths Basic [MCQ]
Last updated at Dec. 16, 2024 by Teachoo
Transcript
Question 7 If cos𝜃 + cos𝜃 + cos〖2 𝜃〗 = 1, the value of sin^2𝜃 + sin^2𝜃 is (a) −1 (b) 0 (c) 1 (d) 2 Given 𝑐𝑜𝑠𝜃 + 〖𝑐𝑜𝑠〗^2𝜃 = 1 𝑐𝑜𝑠𝜃 = 1 − 〖𝒄𝒐𝒔〗^𝟐𝜽 𝑐𝑜𝑠𝜃 = 〖𝑠𝑖𝑛〗^2𝜃 〖𝒔𝒊𝒏〗^𝟐𝜽 = 𝒄𝒐𝒔𝜽 Now, 〖𝑠𝑖𝑛〗^2𝜃 + 〖𝑠𝑖𝑛〗^4𝜃 = 𝒄𝒐𝒔𝜽 + 〖𝒄𝒐𝒔〗^𝟐𝜽 = 1 So, the correct answer is (c)