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Archy [21]
3 years ago
12

Verify as an identity: cos(90°+x) = -sinx I'm not sure how to go about this question

Mathematics
1 answer:
erastovalidia [21]3 years ago
3 0
Cos( a + b ) = cosa×cosb - sina×sinb ; 
a = 90 and b = x ;
But, cos90 = 0 and sin90 = 1;
cos( 90 + x ) = 0 × cosx - 1 × sinx = - sinx ; 
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