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Grade 11Trigonometry

I did not understand a step in the solution of this question... The step which has a box around it. How did that come?

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Profile image of Harnoor
7 Years agoGrade 11
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1 Answer

Profile image of Aditya Gupta
ApprovedApproved Tutor Answer7 Years ago
LHS of the box part came because of the expansion of cos(a+-b).
For RHS, write 1-tanc/1+tanC as cosc-sinc/cosc+sinc. Now multiply the denominator and numerator by 1/√2, coz sin(pi/4+c)= (sinc+cosc)/√2.

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