Question

answer this plz ..........with explanation

Answer 1

sin51° + cos81°,

sin(90°-39°) + cos81°

cos39° + cos81°,

we can write it as,

cos81° + cos39°,

2 cos(81°+39°)/2 . cos(81°-39°)/2,

2 cos120°/2 . cos42°/2,

2 cos60° . cos21°,

2 × 1/2 . cos21°,

cos21°✓✓✓✓✓✓

since cosC + cosD = 2 cos(C+D)/2 . cos(C-D)/2

Answer 2

hey here is ur answer in attachment