Question

If cosA+cos2A=1,then sin2A+sin4A =?

Answer 1

Answer:

Step-by-step explanation:

cos a + cos2 a=1

we have to find the value of Sin2 a + sin4 a

as Sin2 a + cos2 a =1

given,

cos a + cos2 a=1

=cos2 a=1- cos2 a=Sin2 a

Sin2 a+ sin4 a

put the value of Sin2 a

=cos a+cos2 a

=1

Answer 2

Given :-

• If cosA+cos2A=1

To find :-

• then sin2A+sin4A

Solution :-

$\: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf \: {sin}^{2}a + {sin}^{4}a \\ \\ \\ \: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf {sin}^{2}a + {sin}^{2} a \: \: {sin}^{2}a \: \\ \\ \\ \: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf \: {sin}^{2}a + (1 - {cos}^{2}a)( - {cos}^{2}a)$

$\: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf \: sin \: a \: + cos \: a \: \\ \\ \\ \: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf \: {sin}^{2}a + {cos}^{2} a \\ \\ \\ \: \: \: \: \: \: \: \: \: \: \: \longrightarrow \sf \: 1$

${\small{\bold{\underline{\therefore\: our \: required \: answer \: is \: \bold{\pink{1}}\: .}}}}$