If f(x)=2x^2-1 evalueate f(cos theta)
Answers
Answered by
3
f(x) = 2x² - 1
put x → cos∅
f( cos∅) = 2cos²∅ - 1
= cos²∅ + cos²∅ - 1
= cos²∅ - { 1 - cos²∅}
= cos²∅ - sin²∅
[ cos²x - sin²x = cos2x use this concept
= cos2∅]
hence,
f(cos∅) = cos2∅
put x → cos∅
f( cos∅) = 2cos²∅ - 1
= cos²∅ + cos²∅ - 1
= cos²∅ - { 1 - cos²∅}
= cos²∅ - sin²∅
[ cos²x - sin²x = cos2x use this concept
= cos2∅]
hence,
f(cos∅) = cos2∅
Similar questions