Дано: cosα = -3/5 ;π < α< 3π/2 .<br>-------
tq(π/4 -α) -?
tq(π/4 -α) =(tqπ/4 -tqα)/(1+tqπ/4 *tqα) =(1 -tqα)/(1+tqα) =
(1-sinα/cosα)/(1+sinα/cosα)=(cosα -sinα)/(cosα +sinα)=
(-3/5 +4/5)/(-3/5 -4/5) = (1/5) / (-7/5)= - 1/7.
т.к. π < α< 3π/2 sinα = - √(1 -cos²α)= - √((1 -(-3/5)²) = - √((1 -9/25)= - 4/5.<br>
ответ : - 1/7.