Question #9ab7b

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Answer 1 · 2017-12-18T16:24:14

Let's see.

Given,

#cosacosb-sinasinb=1#

#:.color(red)(cos(a+b)=1))#

#:.sin(a+b)=0#

#:.color(red)(sinacosb+cosasinb=0)#......(1).

Now given #rarr#

#color(red)(1+cotatanb)#

#=1+(cosasinb)/(sinacosb)#

#=(sinacosb+cosasinb)/(sinacosb)#

#=color(red)(0)#........From (1).

Hence Proved.

Hope it Helps:)