` theta ` का मान ज्ञात कीजिए यदि ` 2 cos theta^(@) = 1 " तथा" 0^(@) lt theta lt 90^(@)` .

Explanation

` 2 cos 3 theta = 1`
`rArr cos 3 theta = (1)/(2)`
` rArr cos 3 theta = cos 60^(@)`
`rArr 3 theta = 60^(@)`
`rArr theta = 20^(@)` .