Bài 2:
Ta có: \(\sin^2a+cos^2a=1\)
=>\(cos^2a=1-\left(\frac{7}{25}\right)^2=1-\frac{49}{625}=\frac{576}{625}=\left(\frac{24}{25}\right)^2\)
=>\(cosa=\frac{24}{25}\)
\(\tan a=\frac{\sin a}{cosa}=\frac{7}{25}:\frac{24}{25}=\frac{7}{24}\)
\(\cot a=1:\frac{7}{24}=\frac{24}{7}\)
Bài 1:
a: \(1+\tan^2a=\frac{1}{cos^2a}\)
=>\(\frac{1}{cos^2a}=1+\left(\frac34\right)^2=1+\frac{9}{16}=\frac{25}{16}\)
=>\(cos^2a=\frac{16}{25}\)
=>\(cosa=\frac45\)
Ta có: \(\sin^2a+cos^2a=1\)
=>\(\sin^2a=1-\frac{16}{25}=\frac{9}{25}=\left(\frac35\right)^2\)
=>\(\sin a=\frac35\)
b: Ta có: \(1+cot^2a=\frac{1}{\sin^2a}\)
=>\(\frac{1}{\sin^2a}=1+\left(\frac{5}{12}\right)^2=1+\frac{25}{144}=\frac{169}{144}\)
=>\(\sin^2a=\frac{144}{169}=\left(\frac{12}{13}\right)^2\)
=>\(\sin a=\frac{12}{13}\)
Ta có: \(\sin^2a+cos^2a=1\)
=>\(cos^2a=1-\frac{144}{169}=\frac{25}{169}\)
=>cosa=5/13
