If 0≤x≤π/2 and 81sin2⁡x+81cos2⁡x=30, then x is equal 

If 0xπ/2 and 81sin2x+81cos2x=30, then x is equal 

  1. A

    π6,π3

  2. B

    π3,5π2

  3. C

    5π6,π6

  4. D

    2π3,π3

    Register to Get Free Mock Test and Study Material

    +91

    Verify OTP Code (required)

    I agree to the terms and conditions and privacy policy.

    Solution:

    Let 81sin2x=y Than,

          81cos2x=811sin2x=81y1

     81sin2x+51cos2x=30 y+81y1=30 y230y+81=0 y=3 or, y=27. 81sin2x=3 or, 27 34sin2x=31 or, 33 4sin2x=1 or, 3 sin2x=14 or, 34 sinx=±12 or, ±32x=π6 or, π3

    Chat on WhatsApp Call Infinity Learn

      Register to Get Free Mock Test and Study Material

      +91

      Verify OTP Code (required)

      I agree to the terms and conditions and privacy policy.