# If 7 sin^2 theta 3 cos^2 theta = 4, prove that, tan theta= 1/root3

2
by amruthisNat

2015-10-20T15:37:25+05:30

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7sin²Ф + 3cos²Ф = 4
⇒ 4sin²Ф + 3sin²Ф + 3cos²Ф = 4
⇒ 4sin²Ф + 3(sin²Ф + cos²Ф) = 4
⇒ 4sin²Ф + 3(1) = 4
⇒ 4sin²Ф = 4 - 3
⇒ 4sin²Ф = 1
⇒ sin²Ф = 1/4
⇒ sinФ = √(1/4)
⇒ sinФ = 1/2
⇒ Ф = 30°

tanФ = tan30° = 1/√3
2015-10-20T16:01:08+05:30

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
7 sin² A  + 3 Cos² A = 4
7 sin² A + 3 (1 - sin²A) = 4
4 sin² A = 1
Sin² A = 1/4
Cos² A  = 1 - 1/4 = 3/4

Tan² A = (1/4) / (3/4) = 1/3

Tan A = + 1/√3  or  - 1/√3

there are two answers for the given exercise.