Apply Power-Reduction Formula: To solve the integral of cos2(t), we can use a power-reduction formula from trigonometry, which states that cos2(t) can be expressed as (1+cos(2t))/2. This will simplify the integration process.
Rewrite Integral Using Formula: Now, we rewrite the integral using the power-reduction formula:f(x)=∫1ln(x2+x−1)21+cos(2t)dt.
Split Integral into Two: Next, we split the integral into two separate integrals: f(x)=21∫1ln(x2+x−1)1dt+21∫1ln(x2+x−1)cos(2t)dt.
Integrate Each Part Separately: We can now integrate each part separately. The integral of 1 with respect to t is simply t, and the integral of cos(2t) with respect to t is (1/2)sin(2t) because the derivative of sin(2t) is 2cos(2t), so we need to multiply by 1/2 to compensate for the derivative of the inside function.f(x)=(1/2)[t] from 1 to t1 + t2 from 1 to t1.
Evaluate Integrals at Limits: Now we evaluate the integrals at the upper and lower limits: f(x)=21[ln(x2+x−1)−1]+41[sin(2ln(x2+x−1))−sin(2)].
Simplify the Expression: Finally, we simplify the expression to get the final answer: f(x)=21ln(x2+x−1)−21+41sin(2ln(x2+x−1))−41sin(2).