Question

If sinA + sin2A = 1 then what is the value of cos2A + cos4A?

a) 0 b) 1

c) -1 d) 2​

Answer 1

Answer:

1

Step-by-step explanation:

sin∅ + sin²∅ = 1  

=> sin∅ = 1 - sin²∅  

=> sin∅ = cos²∅  

[ Squaring both side ]  

=> sin²∅ = cos⁴∅                     ( i )

cos²∅ + cos⁴∅ .

= cos²∅ + sin²∅ . [ Using ( i ) ]  

= 1 .

[  sin²∅ + cos²∅ = 1 . ]