Question

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1/sin^2α - 1 = ctg^2α​

Answer 1

$\frac{1}{sin^2a}-1=\frac{1-sin^1a}{sin^2a}=\frac{cos^2a}{sin^2a}=(\frac{cosa}{sina})^2=ctg^2a\\\\ili\\\\Formyla:\; \; \; \boxed {1+ctg^2a=\frac{1}{sin^2a}}\; \; \; \Rightarrow \; \; \; ctg^2a=\frac{1}{sin^2a}-1$