Answer:
3. missing angle is 35°
M=cos∧-1(5/7.8)=50.13°
N=180°-90°-50.13°=39.87°
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Step-by-step explanation:
1. 10
2. 26.6
n/2[2a+(n-1)d]
12/2[2(-5)+(12-1)6]
66-10=56×6=336
336 is the 12th term