यदि है ` theta = 18^(@)` , तो ` 4 sin ^(2) theta + 2 sin theta` का मान क्या है ?

Options

A. `-1`
B. 1
C. 0
D. 2

Answer

b

Explanation

` :' theta = 18^(@)`
अब , `4 sin ^(2) theta + 2 sin theta `
` 4 sin ^(2) (18^(@)) + 2 sin (18^(@))`
` [ :' sin 18^(@) = (sqrt(5) -1)/4]`
` 4 { (sqrt(5)-1)/4}^(2) + 2{(sqrt(5)-1)/4}`
` = ( 4(5 +1-2sqrt(5)))/16 + (sqrt(5)-1)/2`
` = ( 3- sqrt(5))/2 + (sqrt(5)-1)/2 = 1 `