Đáp án+Giải thích các bước giải:
`a)P=sin^{2}1^o +sin^{2}2^o +sin^{2}3^o +......+sin^{2}88^o +sin^{2}89^o`
`=(sin^{2}1^o +sin^{2}89^o)+(sin^{2}2^o +sin^{2}88^o)+....+(sin^{2}44^o +sin^{2}46^o)+sin^{2}45^o`
`=underbrace{1+1+....+1}_{\text{44 số 1 do có 44 cặp}}+(1/sqrt2)^2`
`=44+1/2=89/2`
`b)Q=tan15^{o}.tan25^{o}.tan35^{o}.tan45^{o}.tan55^{o}.tan65^{o}.tan75^{o}`
`=(tan15^{o}.tan75^{o}).(tan25^{o}.tan65^{o}).(tan35^{o}.tan55^{o}).tan45^o`
`=(tan15^{o}.cot15^{o}).(tan25^{o}.cot25^{o}).(tan35^{o}.cot35^{o}).tan45^o`
`=1.1.1.1=1`
