Question

cos48'.cos12′ =√5+3/a
Then a =
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Answer 1

Step-by-step explanation:

Given Cos48 x cos12′ =√5+3/8

• So we have cos theta x cos (60 – theta) x cos (60 + theta) = ¼ cos 3 theta
• Now cos (60 – theta) cos 12 cos (60 + 12) / cos (60 + 12) (so multiply and divide)
•         = ¼ cos 3 x 12 (since theta = 12 degree) / cos 72
• So we get ¼ cos 36 degree / cos 72 degree
•                 ¼ cos 36 / cos (90 – 18)
•                ¼ cos 36 / sin 18
•               ¼ √5 + 1 / 4  / √5 – 1 / 4 ( solving for cos 36 and sin 18)
•                ¼ √5 + 1 / √5 – 1
•      Rationalizing wit te denominator we get
•                ¼ (√5 + 1 / √5 – 1) (√5 + 1 / √5 + 1)
•                  ¼ (√5 + 1)^2 / 5 – 1
•                  ¼ ( 5 + 1 + 2√5 ) / 4
•                  1/16 (6 + 2√5)
•                  We get 3 + √5 / 8

Reference link will be

https://brainly.in/question/2791356

Answer 2

Answer:

we will get 3+√5/8 hope it helps you