Question

prove that (sinA+cosA)^2-(sinA-cosA)^2=4 sinA cosA

Answer 1

Step-by-step explanation:

(a+b)²=a²+b²+2ab

(a-b)²=a²+b²-2ab

from. above eqns

(a+b)²-(a-b)²=4ab ---(1)

put a=sinA

b=cosA in eq(1)

we get

(sinA+cosA)²-(sinA-cosA)²=4 sinA cosA