We will start by expanding the left-hand side (LHS) of the equation:
(1+tanA)2+(1+cotA)2=(1+2tanA+tan2A)+(1+2cotA+cot2A) =2+2tanA+2cotA+tan2A+cot2A We know the following trigonometric identities:
tanA=cosAsinA cotA=sinAcosA secA=cosA1 cscA=sinA1 sin2A+cos2A=1 tan2A+1=sec2A cot2A+1=csc2A From the Pythagorean identities, we can replace tan2A and cot2A in our expression: tan2A=sec2A−1 cot2A=csc2A−1 Substituting these into our expression, we get:
2+2tanA+2cotA+tan2A+cot2A=2+2tanA+2cotA+(sec2A−1)+(csc2A−1) =2+2tanA+2cotA+sec2A−1+csc2A−1 =2tanA+2cotA+sec2A+csc2A Now, let's expand the right-hand side (RHS) of the equation:
(secA+cscA)2=sec2A+2secAcscA+csc2A Now, we need to show that 2tanA+2cotA=2secAcscA. Let's rewrite 2tanA+2cotA: 2tanA+2cotA=2cosAsinA+2sinAcosA=2(sinAcosAsin2A+cos2A)=2(sinAcosA1) Since secA=cosA1 and cscA=sinA1, then secAcscA=cosAsinA1. Therefore, 2secAcscA=sinAcosA2. So, 2tanA+2cotA=2secAcscA. Thus, the left-hand side is 2tanA+2cotA+sec2A+csc2A=2secAcscA+sec2A+csc2A. And the right-hand side is sec2A+2secAcscA+csc2A. Therefore, (1+tanA)2+(1+cotA)2=(secA+cscA)2 is true.