sin a=(3)/5 ; cos B=(8)/17;
(n)/2>a<n ; 0<B<(n)/2; Знайти sin(a+B);
cos ² B = 1-sin ² B
(8/17 )²= 1- sin ² B
1- sin ² B = (8/17 )²
1- sin ² B = 64/ 289
- sin ²B= 64/ 289 -1
- sin ²B= - 225 /64
sin ²B= 225 /64
sin B= √ ( 225 /64)
sin B= 15/ 8
sin (A+B)= 3/ 5 + 15/ 8 = 99/40 = 2 целых (19/40)
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cos ² B = 1-sin ² B
(8/17 )²= 1- sin ² B
1- sin ² B = (8/17 )²
1- sin ² B = 64/ 289
- sin ²B= 64/ 289 -1
- sin ²B= - 225 /64
sin ²B= 225 /64
sin B= √ ( 225 /64)
sin B= 15/ 8
sin (A+B)= 3/ 5 + 15/ 8 = 99/40 = 2 целых (19/40)