Alfa=beta, gama=alfa+102
alfa+beta+gama=180
alfa+alfa+alfa+102=180
3alfa=78, alfa=beta =78/3 = 26
alfa=26,beta=26, gama=128
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Cos²a+sin²a=1 |:cos²a
1+tg²a=1/cos²a
ctg²a+1=1/sin²a
tg²a+ctg²a+2-(1+tg²a)=tg²a+ctg²a+2-1-tg²a=ctg²a+1=1/sin²a