Question

sin a + b is equal to sin a into cos b + cos b into sin a find the value of sin 75 degree​

Answer 1

Answer:

this is simple babe .

let me tell you the procedure .

75 = 30+45

take a as 30 and b as 45

now substitute.

sin (30+45) ==> sin30cos45 + cos30sin45

now

sin75 ===> 1/2× 1/√2 + √3/2×1/√2===> (√3 + 1)/2√2

Answer 2

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sin( A + B ) = sinAcosB + cosAsinB

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1) Here , we assume

A = 45° , B = 30°

cos 15°

= cos ( 90 - 75 )

= sin 75°

= sin ( 45 + 30 )

= sin45cos30 + cos45sin30

= ( 1√2 )( √3/2 ) + ( 1/√2 )( 1/2 )

= ( √3/2√2 ) + 1/2√2

= ( √3 + 1 ) / 2√2

Therefore,

cos15° = sin75° = = ( √3 + 1 ) / 2√2