cos4a-sin4a=cos2a-sin2a
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(cos2a + sin2a ) (cos2a - sin2a )
(a+b) (a-b) = a² - b²
1(cos2a - sin2a )
lhs = rhs
(a+b) (a-b) = a² - b²
1(cos2a - sin2a )
lhs = rhs
Tina11111:
u too
Answered by
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cos⁴a – sin⁴a = cos²a – sin²a
L.H.S.
cos⁴a – sin⁴a
{by using identity
a⁴– b⁴ = (a²)² – (b²)² = (a²+ b²) ( a² - b²) }
so
= (cos²a + Sin²a) (cos²a – sin²a)
{ we know that
sin²a + cos²a = 1 }
therefore
= 1 × ( cos²a – sin²a)
= cos²a – sin²a
= R.H.S.
Hope, it may help you.✌️✌️
L.H.S.
cos⁴a – sin⁴a
{by using identity
a⁴– b⁴ = (a²)² – (b²)² = (a²+ b²) ( a² - b²) }
so
= (cos²a + Sin²a) (cos²a – sin²a)
{ we know that
sin²a + cos²a = 1 }
therefore
= 1 × ( cos²a – sin²a)
= cos²a – sin²a
= R.H.S.
Hope, it may help you.✌️✌️
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